This interesting electronic project allows you to clearly hear a world of sounds beyond the limits of human perception. The ultrasonic microphone that you will create (Fig. 26.1) has a very wide range of household and technical applications: from detecting leaks of gases, liquids, mechanical wear of bearings, rotation mechanisms and reciprocating motion, for example, in cars, to detecting electrical leaks in insulators power lines. The entire world of sounds of living beings also becomes audible. Simple events - a cat walking on wet grass, the jingling of a key chain, even a plastic bag bursting - can be heard very clearly. On a warm summer night, a chorus of wonderful sounds can be heard as nature's orchestra of creatures ranging from bats to insects creates a cacophony of natural sounds beyond the range of the human ear, and the ultrasonic microphone makes inaudible sounds audible.
This handheld directional microphone easily detects and converts ultrasonic vibrations into sound. The addition of a parabolic reflector further enhances the capabilities of this device. Expect to spend between $30 and $50 on this cost-recovery device.
This project allows you to listen to the world of sounds, the existence of which few people know. The device is made in the form of a pistol, in the barrel of which there is an electronics unit. The rear panel contains switches and a volume control, a variable resistance trimmer and a headphone jack. The front of the device is a directional receiving transducer. The handle contains batteries.
The addition of a parabolic reflector option increases the directivity of the ultrasound source, providing ultra-high gain and greatly enhancing the device's long-distance sound reception capabilities.
Rice. 26.1. Ultrasonic microphone with parabolic reflector
Application of the device
One of the most interesting sources of ultrasonic mechanical vibrations are many species of insects that produce mating and warning signals. On a typical summer night, you can spend many hours listening to bats and other strange noises made by flora and fauna. A whole world of natural sounds awaits the user of the device. Many artificial sounds are also sources of ultrasonic vibrations and are recorded by the device. Below are a few examples, but these are just a few of the potential sources of ultrasound:
Gas leakage and air flow;
Water from spray bottles in case of leakage from the device;
Corona discharge, spark discharge or lightning generating devices;
Fires and chemical reactions;
Animals walking on wet grass and creating rustling sounds. This is a great tool for hunters and spotters, or just a way to find your pet at night;
Computer monitors, television receivers, high-frequency generators, mechanical bearings, strange sounds in cars, plastic bags, jingling coins.
The demonstration of this ultrasonic microphone also shows the use of the Doppler effect, where movement towards the source causes an increase in frequency, and movement away from the source causes a corresponding decrease in frequency.
The Doppler effect occurs when an observer moving towards a sound source perceives an increasing frequency. This is easy to imagine if you understand that sound travels in the form of a wave at a relatively constant speed. When an observer moves towards a sound source, he intercepts more waves in a shorter period of time, thus hearing a sound that appears to have a shorter wavelength or, correspondingly, a higher frequency. If it moves away from a sound source, a lower pitch frequency is heard compared to the frequency heard by a stationary observer.
To provide entertainment for both adults and children, you can hide a small test ultrasound generator and challenge your opponent to find it in the shortest possible time.
Basic diagram of the device
The microphone of the ultrasonic piezoelectric transducer TD1 perceives ultrasonic mechanical vibrations and converts them into an electrical signal due to the piezoelectric effect (Fig. 26.2). Coil L1 and the piezoelectric transducer's own capacitance form an equivalent resonant circuit at a resonance frequency of about 25 kHz. A resistor Rd is connected in parallel to the circuit. This parallel equivalent resonant circuit forms a high-impedance signal source, which is connected through the capacitor C2 to the gate of field-effect transistor Q1. Resistor R1 and capacitor C1 decouple the drain bias voltage. Circuit design and shielding of input wires play an important role here, since this circuit is very sensitive to noise, feedback signals, etc.
The signal from the output of load resistor R2 of transistor Q1, through the isolation capacitor SZ and resistor R4, is supplied to the input of amplifier I1A with a dimensionless gain equal to 50 and determined by the ratio of the resistances of resistors R6/R4.
Output I1A through capacitor C4 is connected via alternating current to mixer-amplifier I1B. The output of the I1C generator is connected to the circuit using a “special device” based on the CM mounting capacitor, created by a short wire from pin 8 of the IC1 element, which is twisted with a similar wire from pin 2 of the IV element (it is proposed to check the operation of the device without this device). The IIC generator produces signals of one of the frequencies, which is mixed with the received signals through the CM at the I1B input. The result will be a mixture of two signals, one of which represents the sum, and the other the difference of these signals, lying in the audio frequency range.
Capacitor C7 and resistor R17 form a bandpass filter that cuts out the sum of frequencies from the frequency mixture and passes the frequency difference at a level of 20 dB. Thus, the resulting low-frequency signal is the difference between the frequencies of the oscillator and the real signal. This is similar to the superheterodyne effect. The filter from C7 and R17 additionally decouples the signal
Rice. 26.2. Schematic diagram of an ultrasonic microphone
Note:
Proper placement of power wires will improve the noise performance of the circuit.
The wires to J1 should be short and as straight as possible.
Power wires must be connected from the back of the circuit board.
Rd is selected to dampen (calm down) the response of the converter. The expected value is 39 kOhm.
If possible, twist the wires into twisted pairs.
high frequency. The filtered signal represents the frequency difference, is rectified by diode D1 and integrated by capacitor C8. The rectified signal is in the audio range and can actually be heard. It is adjusted using a variable resistor R12 in the generator section and allows selective tuning to specific frequencies within the permissible range of the piezoelectric transducer TD1. The resulting audio frequency signals are supplied to the volume control R19 through the DC blocking capacitor SY. Capacitor C12 additionally filters out the remaining high-frequency signals. From the middle terminal of variable resistance R19, an audio signal is supplied to headphone amplifier 12 with an output impedance of 8 Ohms. The signal from output 12 is fed through capacitor C16 to the headphone jack J1. The power gain of 12 is small, and in addition to headphones, you can connect a low-power 8-ohm speaker to jack J1 for group listening. Filter R21/C4 further attenuates high frequencies.
Power supply 12 is isolated using resistor R20 and capacitor C15. This ensures circuit stability and prevents oscillations in the feedback loop and other unwanted effects.
The operating point of I1A, I1B, I1C is set to the average value of the supply voltage using a resistive divider R7/R11. Resistors R5, RIO, R15 compensate for the bias current.
Device assembly procedure
When assembling the device, first perform the operations of assembling the breadboard with perforation of holes, then other sections of the device structure:
1. Organize the components by ratings and purpose (separately resistors, capacitors, etc.) and check them with the specification (Table 26.1).
Table 26.1. Ultrasonic Microphone Specification
|
Designation |
Qty |
Description |
No. in database |
Resistor 10 Ohm, 0.25 W (brown-black-black) |
Resistor 3.9 kOhm, 0.25 W (orange-white-red) |
Resistor 10 MΩ, 0.25 W (brown-black-blue) |
Resistor 10 kOhm, 0.25 W (brown-black-orange) |
Variable resistance YukOhm, 17 mm |
R5, R7, R10, R11.R14.R15 |
Resistor 100 kOhm, 0.25 W (brown-black-yellow) |
Resistor 470 kOhm, 0.25 W (yellow-purple-yellow) |
Resistor 2.2 kOhm, 0.25 W (red-red-red) |
Resistor 1 MΩ, 0.25 W (brown-black-green) |
Resistor 4.7 kOhm, 0.25 W (yellow-purple-red) |
Variable resistance YukOhm, 17mm, slide type/switch |
Resistor 47 Ohm, 0.25 W (Yellow-Purple-Black) |
Resistor 10-47 kOhm (selectable, selected for the damping converter circuit), 0.25 W |
Electrolytic capacitor 10 µF, 25 V vertical installation |
C2.C3.C4, C6, C10, C12 |
Disc or plastic capacitor 0.01 µF, 25 V |
C5, C7, C13, C14 |
Disc or plastic capacitor 0.1 µF, 25 V |
Plastic capacitor 0.047 µF, 50 V |
Electrolytic capacitor 100 µF, 25 V vertical installation |
Electrolytic capacitor 1000 µF, 25 V vertical installation |
Silicon diode IN914 |
Inductive coil 27 mH |
Field-effect transistor J202 (FET) |
Operational amplifier LM074 in DIP package |
ULF LM386 in DIP package |
3.5mm stereo audio jack connected in Mono mode |
Receiving acoustic transducer 25 kHz |
Shielded microphone cable |
RSV printed circuit board or breadboard measuring 5.06×5.06 cm with perforation of holes in 0.25 cm increments |
Thin sheet of plastic 5.06 x 5.06 cm for insulation |
Neoprene bushing 2.54×1.27×0.48 cm |
Battery clamp with 30 cm leads |
Parabolic reflector option |
PCB option RSV |
2. Insert the components starting from the left side of the perforated breadboard, following the layout shown in Figure. 26.3, to connect the board to other sections of the structures and using the 2 holes on the bottom right as guides. The board has dimensions of 5.72 × 5.72 × 0.25 cm. Instead, you can use a board with printed wiring of RSV conductors, which can also be purchased through the website www.amasingl.com. When making connections, use the component pins; connections between components are made on the back of the board (shown with a dotted line). On the component installation side there are connections shown as a solid line. It is recommended to try on larger parts before starting to solder their leads.
Always avoid jumpers made of bare wire, poor-quality solder joints, and possible short circuits due to soldering. Check the device circuit components for cold solder joints and poor solder joints.
Pay attention to the polarity of the capacitors, on the body of which the “+” sign indicates positive polarity, the other terminal of the polar capacitor will have, accordingly, negative polarity,
Rice. 26.3. Breadboard assembly
as well as the polarity of all semiconductor devices. The pinout of each microcircuit is determined by a key in the shape of a semicircle and the output of microcircuit 1 to the left of the key. The terminals of the variable resistances and socket J1 must physically match the holes for their installation in RP1.
3. Cut, strip and tin the wires to connect to J1 and solder them. These wires should be twisted and 5.08 cm long.
4. Make chassis CHAS1, front panel RP1, body EN1 and handle HAND1 as shown in Fig. 26.4.
Rice. 26.4. General view of the sections of the collection device structures, with the indicated dimensions for manufacturing
Rice. 26.5. Installing the breadboard on the chassis and external board connections
Note:
It is very important to ensure proper heat dissipation from the contacts of the TD1 converter before starting soldering. When in doubt, use nuts or slip-on connections to dissipate heat. Note that the short pin is internally connected to the converter body and to circuit ground. If there is no short circuit between this contact and the aluminum body of the converter, then this converter will be damaged as a result of overheating!
You can use a battery of 6 AAna9Vilina12V cells using 8 AA cells, which is placed in the HA1 handle. The 12V power supply allows you to increase the sound output of a low-power 8 Ohm speaker and its volume.
5. Prepare both ends of the shielded cable as follows. If the parabolic reflector option is used, you will need 45 cm of cable, if not, 15 cm (Fig. 26.5).
Rice. 26.6. The final design of the device using a reflector
Note:
The shielded cable is 45 cm long and passes through a small hole in the rear cover of the SARZ and the PARA12 reflector.
TD1 is placed in bushing BU1. This assembly is then inserted into the inside of a 13.2 cm long, 4.13 cm outer diameter cylindrical housing using O-rings. This placement of TD1 secures the transducer and protects it from shock.
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The converter connections are made in accordance with Fig. 26.5.
– carefully remove 1.9 cm of outer insulation, but so as not to damage the screen braid;
– cut through the screen braid with a sharp object, such as a pin, and twist the wire out of it. Gently tin only the ends to hold the strands together;
– carefully strip 0.64 cm of insulation from the central wire and tin it;
– check the finished cable for shorts or leaks using a multimeter in resistance measurement mode.
6. Solder coil L1, contacts of the piezoelectric transducer and damping resistor Rd to each other in parallel, as well as the ends of cable SH1 (central core to one common point, cable braid to another), see fig. 26.5. When soldering, be careful not to overheat the converter contacts or the center conductor insulation. If the contacts overheat, the component, especially the piezoelectric transducer, as discussed above, will fail. You can do a simple test on
Rice. 26.7. View of the assembled device design without using a reflector
short circuit between the metal body of the component and the shortest terminal. If the resistance is higher than 1 ohm, this means that you have damaged this part and it needs to be replaced. Mechanical connections using twisted harness, wire nuts, etc. shown above (see Fig. 26.5).
7. Assemble the device as shown. An assembly using a parabolic reflector is shown in Fig. 26.6, and in Fig. 26.7 – without it.
Preliminary electrical tests
To check the functionality of the system, follow these steps:
1. Turn off the device, connect the HS30 headphones, insert the 9V battery. Connect the multimeter in 100mA current mode to the contacts of switch R19 and quickly measure the current, which should be about 20mA. Turn off the multimeter and set the R19 regulator to the middle position. Notice the soft hissing sound in the headphones. Then turn on your computer or TV and configure the R19 to receive a clear tone signal from one of these audio sources. Turn off the sound source and gently rub two fingers together while listening to a clearly audible sound through the headphones. Check the entire range of the controller for unwanted feedback or false signals.
The device is now ready for final assembly. Pay attention to the test points and waveforms (see Figure 26.2). The shape and amplitude of the signals must correspond to those shown in Fig. 26.2.
2. Complete the final assembly by adding the PARA12 parabolic reflector to significantly increase the instrument's range (see Figure 26.6).
Please be aware that your device may sense strong magnetic fields because it is not shielded from them. Performing the Doppler effect test described above makes it easy to distinguish between these fields.
Special Note: Using a Standing Wave
It is possible to form a standing wave in front of the TD1 piezoelectric transducer and improve the sensitivity of the system. Point the instrument at a stable, low-intensity ultrasonic energy source and carefully adjust the distance to the 2.54 x 2.54 cm metal plate mounted in front of the transducer face, observing the signal increase as it approaches the piezo transducer. This effect will occur in half-wave multipliers and is most pronounced near the converter. Use your own creativity to modify this simple action.
Additional notes regarding the use of the device
The device can provide many hours of fun for adults and children. For example, you can hide a small box with a 25 kHz frequency generator somewhere. The narrow radiation pattern of the device and its ability to register different signal levels will allow you to quickly detect this hidden source by the participants of the game, in turn, with jokes and jokes! Please note that the range of the device can exceed 400 m! This gives you a lot of options for choosing where to place your generator cache, and your imagination will tell you how to make it difficult to find. I have spent many enjoyable times with my children and friends using this equipment in play.
Recording the output signal
You can easily record the output signal using a recording device by connecting the auxiliary input to the headphone output jack. For simultaneous listening while recording, the “U” adapter can be used. With the adapter, you can use two sets of headphones with an output impedance of 8 ohms.
Schematic diagram of a homemade device for listening to ultrasonic acoustic waves. As you know, the human ear is not capable of hearing sound with a frequency of more than 20 kHz. Acoustic vibrations of a higher frequency are ultrasound. They can range in frequency from 20 kHz to hundreds of kHz and even down to 1 MHz.
But the statement that we do not hear ultrasound is not entirely true. Our hearing organs, and our entire body, certainly react to it, but we cannot understand this.
This is why ultrasound can have both positive and negative effects on us. For example, in an area where there is a fairly powerful ultrasound source, it seems to us that we are in silence, but at the same time we quickly get tired, our hearing becomes dull (obvious overload of the hearing organs), a headache or a feeling of stuffy ears, dizziness may appear.
Here we describe a device that allows you to hear ultrasound, in the literal sense, to hear it, and not to register its presence.
The device reduces the frequency of the input audio signal to a level we can hear, doing this by frequency conversion. In practice, this is an ultrasonic superheterodyne receiver that converts the input signal, ultrasound, into a low “intermediate” frequency accessible to our perception.
Schematic diagram
The circuit diagram of the device is shown in Figure 1. A local oscillator frequency generator is made on the A1 chip; this frequency should differ from the ultrasound frequency that we want to hear by 1-10 kHz, that is, to a frequency that is clearly audible to our human ear. The frequency is controlled by variable resistor R1 within the range of approximately 25 to 50 kHz.
If it is necessary to cover a larger range, you can switch capacitors C1, choosing them of different capacities, so that the switch can be used to switch subranges.
The local oscillator signal, in the form of rectangular pulses, is supplied to the frequency converter through a divider on resistors R3 and R4, which reduces the amplitude of these pulses.
Rice. 1. Schematic diagram of a device that allows you to hear ultrasonic acoustic waves.
The frequency converter is made on an A2 microcircuit of type SA602. This microcircuit is widely known to radio amateurs and is usually used in a radio reception circuit as a frequency converter. Here it also works as a frequency converter.
Its input receives a signal from microphone M1, and its local oscillator input receives a local oscillator signal from the local oscillator on the A1 chip.
Naturally, the output will be a total difference signal; it comes from pin 5 of A2 through the volume control R5, to the ULF on the AZ chip. Circuit R7-C12 serves as a simple low-pass filter that suppresses the total signal.
As a result, only the difference signal is sent to the ULF on the AZ microcircuit. Which is then amplified and voiced by B1 headphones.
The ULF on the AZ chip type LM386 operates in maximum gain mode with a gain of 200. You can also install a speaker at the output, but you need to monitor the volume so that self-excitation does not occur.
If you have a good laboratory generator of a sinusoidal or square wave signal, from which you can obtain a frequency ranging from 20 kHz to 1 MHz, then it would be preferable to use it as a local oscillator.
In this case, the circuit takes the form as shown in Figure 2. Using such a device, you can listen to almost the entire ultrasonic range for the presence of ultrasound. In the diagram in Fig. 2, the numbering of parts is preserved as in Fig. 1.
Rice. 2. Diagram of a device for listening to ultrasound using an external signal generator as a local oscillator.
The scheme can, of course, be modified. For example, a generator on a 555 type A1 chip (the so-called integrated timer) can be replaced with a multivibrator circuit on a logic chip, for example, K561LA7, as shown in Figure 3. This circuit allows you to adjust the frequency with a continuously variable resistor R2 from 25 kHz to 400-500 kHz.
Other options for the local oscillator circuit are also possible. Microphone M1, of course, it is advisable to use a special one for the ultrasonic range. But, in the absence of one, a high-frequency dynamic head will do.
Of course, its sensitivity as a microphone will be a little low, but it is quite sufficient if you listen to the signal on headphones (B1).
It is advisable to equip the microphone with a parabolic horn so that it is more convenient to localize the ultrasound source. It should be taken into account that when using a high-frequency dynamic head as a microphone, the sensitivity will decrease even more, the higher the frequency of the ultrasound that needs to be listened to.
Rice. 3. Signal generator circuit based on the K561LA7 microcircuit.
The device was manufactured for experimental purposes, so it was assembled on a printed breadboard. A special printed circuit board was not developed for it.
Rice. 4. Schematic diagram of an ultrasonic acoustic signal generator.
No configuration is required, it works immediately after switching on. For testing, an ultrasound generator was assembled according to the diagram in Fig. 4.
Podgornoe A. RK-01-18.
Radioconstructor 2007 No. 2
Ultrasounds surround us everywhere; these can be the “negotiations” of animals, the noise of various equipment, as well as ultrasounds specially generated by echo sounders and medical devices. Unlike sounds in the audible range, ultrasounds affect us imperceptibly. And not always favorable. A clear example is that in a certain place, for example, near some equipment, you have a headache and your hearing is somehow reduced. All the symptoms of deafening, but there is silence all around. Apparent silence. “Decibels” of the ultrasonic range are pressing on your ears, they deafen you, but you cannot understand this, because you do not hear the acoustic vibrations interfering with you.
Using this simple device, you can not only determine the source of ultrasound and its intensity, but also “listen” to the ultrasound, determine the nature of its sound (intermittent, with changing frequency, etc.).
The basis of the device is the ultrasonic microphone MA40B8R (M1). The number “40” in its name indicates the frequency (40 kHz) at which it has maximum sensitivity. At frequencies below 32 kHz, sensitivity drops sharply (-90dB). This sensitivity characteristic makes it possible to use it for monitoring ultrasound without the use of special filters that suppress sound frequencies.
The ultrasonic level indicator circuit consists of a microphone M1, a two-stage amplifier on transistors VT1 and VT2 and an alternating voltage meter on diodes VD1, VD2 and a dial indicator MA. The alternating voltage from Ml is supplied to a two-stage amplifier through the sensitivity regulator R7. The amplified AC voltage is then detected by diodes VD1 and VD2. A constant voltage is generated at capacitor C6, proportional to the ultrasound volume level. This voltage is shown by the MA dial gauge.
To listen to ultrasound, a method is used to reduce its frequency to frequencies in the audio range by dividing it with a digital counter.
From collector VT2, an alternating voltage of ultrasonic frequency is supplied to the pulse shaper on transistor VT3. The transistor is turned on without bias at the base and opens like an avalanche when the amplitude of the alternating voltage at its base exceeds the opening barrier of the transistor.
Pulses from the VT3 collector are supplied to the counting input of the binary counter D1. The counter divides their frequency by 128. Then, from the output of the counter, pulses are sent to the headphones.
As a result, for example, ultrasound with a frequency of 40 kHz is reproduced by headphones as a sound with a frequency of 312.5 Hz (40/128 = 0.3125). Now we can “hear” ultrasounds, monitor changes in their frequency, and determine their intensity using a dial indicator. The disadvantage is that the sound volume in the headphones does not depend on the ultrasound volume, but this is compensated by the dial level indicator.
Most of the parts are installed on a printed circuit board made of fiberglass with one-sided foil. The board is placed in a plastic case and located along it. Next to it, in a hole specially cut into the body, there is an imported dial indicator (similar to the M470 indicator) with an end position of the scale. The total deflection current of the indicator needle is 300mA, and the resistance is 1200 Ohms. However, you can use any similar microammeter, with a scale of no more than 400mA and a resistance of at least 300 Ohms. Its sensitivity can be adjusted by connecting an additional resistor in series, the resistance of which will need to be selected experimentally.
The K561IE20 chip can be replaced with the K561IE16 counter. In this case, the output will be not the 4th, but the 6th pin of the microcircuit (you need to slightly change the printing of the board).
The power switch is a microswitch mounted by soldering onto the board. At the same time, the nut for fastening the toggle switch to the panel serves as an element for fastening the board in the case. Connector X1 is a socket for small-sized stereo headphones; it is also installed on the board. The connection diagram of this connector is such that the headphones operate in series.
The power source is a 9V Krona battery.
The adjusted resistor R7 can be replaced with a variable one, then it will be possible to adjust the sensitivity of the device within a wide range.
The printed circuit diagram of the board and the wiring diagram are shown in Figure 2, and Figure 3 shows how the device parts are placed in the housing.
Figure 2. Printed circuit board
Figure 3. Wiring diagram.
Figure 4. Layout diagram.
The amplification stages on transistors VT1 and VT2 need to be adjusted. Having set the adjusted resistor to the minimum sensitivity position (slider down all the way, according to the diagram), you need to measure the constant voltages on the collectors VT1 and VT2. If these voltages go beyond 2.5-3V, you need to select the resistance of the base resistors (R1 and R2, respectively).
There are sounds that only a small part of people can hear. While some may not even be aware of their existence, for others it is a serious problem. The sounds are so loud that they cause irritation and headaches in people sensitive to them. We are talking about ultrasonic waves here. Scientists still cannot decide how widespread they are and what harm they cause to society.
Timothy Layton
The ultrasound class was the subject of more than ten years of research by Timothy Leighton, a professor of acoustics. He spoke about the results of his work relatively recently - on May 9, 2018.
Who hears ultrasound?
Layton said in an interview that not every one of us can hear ultrasound. This is too high a frequency for the human ear. But in practice, the ultrasonic wave can be felt for the following categories:
- Newborn children.
- Teenagers and young adults.
- Men and women with extremely acute hearing.
The problem of those sensitive to ultrawaves
For all these people, ultrasound is a fairly serious problem. It is aggravated by the fact that to date it has been little studied. Timothy Leighton says that people come to him who feel unwell in certain buildings. It seems to them that they are constantly surrounded by unpleasant, continuous oppressive sounds.
With a similar problem, people are sent to have their hearing checked by an ENT specialist, who, of course, does not find any abnormalities. This makes the patient think that these sounds are only in his head, as if he is going crazy, hearing something that is not in reality.
Researching a problem in the scientific world
The problem is that very few scientists devote themselves to ultrasound research. Timothy Leighton says there are at most six researchers in the world working on this issue. This circumstance explains the large number of people who want to see him for a consultation.
The above does not mean that the scientist’s works are not included in the scientific mainstream. Layton was one of two co-chairs invited to a session on high-frequency audio as part of the ASA meetings. For his research, the scientist received the Clifford Paterson Award from the Royal Society (for selected research in the field of underwater acoustics).
It is important to highlight that most scientists studying ultrawaves do not direct their work to determine how these sounds affect humans. When journalists turned to Layton’s colleagues to comment on the problem raised, they honestly admitted that they did not have sufficient knowledge to reason in this vein. 
Layton's research
Yes, ultrawaves are everywhere. Can you hear them? Professor Layton - no. However, he is concerned about the problems of people sensitive to ultrasound. The scientist went to study ultrawaves in buildings where his visitors felt unpleasant symptoms. Using special instruments, he established the presence of ultrasound inside these rooms.
What's sad is that these are public places that are visited by 3-4 million people a year. Therefore, there is a high probability that among them there will be a considerable number of people sensitive to sound. When exposed to ultrawaves, these people experience unpleasant symptoms: headache, ringing in the ears, nausea, noise in the head. As soon as you leave the room, the manifestations weaken. After about an hour, the person already feels normal.
Unfortunately, today illness caused by ultrasound is considered something of quackery and superstition. After all, scientists simply have no idea how these sound waves affect the human body. 
Mass ultrasonic exposure
The issue may also be unpopular because the number of people affected by ultrasound is relatively small on a global scale. But still, there have been high-profile events in history associated with its negative impact.
Leighton gives an illustrative example. American diplomats who arrived in Cuba began to suffer en masse from a complex of symptoms experienced by people sensitive to ultrasound. They complained of persistent headaches, suffered from tinnitus and even hearing loss. It is believed that a secret ultrasonic weapon was used against them.
Timothy Leighton believes that the negative impact of ultrasound on humans is a global problem. And the point is not that it brings suffering to a small group of people sensitive to ultrasonic waves. Ultrasound has a detrimental effect on everyone, especially young people. Only people who are insensitive to it do not notice it and attribute unpleasant symptoms to another cause. 
Why can't everyone hear ultrasound?
Research on the sensitivity of the human ear to various sound waves was carried out back in the 1960s and 70s. Scientists needed to find out what kind of sound exposure in the workplace is considered acceptable and acceptable for work. It was then determined that ultrasound is not a problem for a worker if its frequency is 20 kHz (or 20,000 vibrations per second).
Why don't we recognize it? This sound is too high for the human ear. Especially for an adult. Once a tone goes above 16 kHz, most people stop hearing it.
But this only applies to adults. If your school years were in the 2000s, you remember how popular the melody “mosquito squeak” was. She annoyed all your classmates, but the teachers didn't hear her. But this was the same ultrasound. It is important to note that men become insensitive to high-range sounds earlier than women. 
Limitations of past studies
Timothy Layton argues that the main flaw in the studies of the 60s and 70s on the permissible effects of ultrasound on the human body is due to the fact that the experiments involved adult men. And from the above it is easy to determine that they did not hear those annoying sounds that young women and children hear.
Therefore, the noise level requirements that guide many countries around the world are completely incorrect. They do not protect people sensitive to ultrasound. A striking example of this: a schoolboy became nervous and irritable because a classmate turned on the “mosquito squeak” on his phone. But the teacher does not hear this sound, he punishes this child for bad behavior without knowing the reason.
Using Ultrasound
Today, ultrasound is successfully used in many public places to repel rodents. It is continuously transmitted through sensors. This is typical for restaurants, train stations, stadiums and other public places.
Motor vehicles are also a source of ultrasound. In addition, it is often used for loudspeaker testing. From this it can be seen that people sensitive to ultrawaves have practically no place to hide from them in the city.
Solving the problem
But Layton is confident that the problem can be solved. The most important thing is to popularize it. After all, people who do not hear ultrasound do not even imagine how it negatively affects others.
The second is to urge manufacturers of devices that transmit ultrasound to focus on modern rather than outdated standards. The scientist himself says that there are already enterprises that are interested in his research and are eliminating the problem.
And thirdly, to popularize the problem in the scientific world. To interest scientists in conducting research in this area. 
If we don't feel a problem, it doesn't mean it doesn't exist. This is what Timothy Layton's research convinces.
If you hear some sounds that other people cannot hear, this does not mean that you are having auditory hallucinations and it’s time to see a psychiatrist. Perhaps you belong to the category of so-called Hamers. The term comes from the English word hum, meaning hum, buzzing, buzzing.
Strange complaints
The phenomenon was first noticed in the 50s of the last century: people living in different parts of the planet complained that they constantly heard a certain uniform humming sound. Most often, residents of rural areas talked about this. They claimed that the strange sound intensifies at night (apparently because at this time the overall sound background decreases). Those who heard it often experienced side effects - headache, nausea, dizziness, nosebleeds and insomnia.
In 1970, 800 Britons complained about a mysterious noise. Similar episodes also occurred in New Mexico and Sydney.
In 2003, acoustics specialist Jeff Leventhal discovered that only 2% of all inhabitants of the Earth can hear strange sounds. Mostly these are people aged 55 to 70 years. In one case, a Hamer even committed suicide because he could not bear the incessant noise.
“It’s a kind of torture, sometimes you just want to scream,” this is how Katie Jacques from Leeds (Great Britain) described her feelings. - It's hard to sleep because I hear this pulsating sound continuously. You start tossing and turning and think about it even more.”
Where is the noise coming from?
Researchers have been trying to find the source of the noise for a long time. In the early 1990s, researchers at the Los Alamos National Laboratory at the University of New Mexico came to the conclusion that hummers hear sounds that accompany traffic and production processes in factories. But this version is controversial: after all, as mentioned above, most Hamers live in rural areas.
According to another version, there is actually no hum: it is an illusion generated by a diseased brain. Finally, the most interesting hypothesis is that some people have increased sensitivity to low-frequency electromagnetic radiation or seismic activity. That is, they hear the “hum of the Earth,” which most people do not pay attention to.
Paradoxes of hearing
The fact is that the average person is able to perceive sounds in the range from 16 hertz to 20 kilohertz, if sound vibrations are transmitted through the air. When sound is transmitted through the bones of the skull, the range increases to 220 kilohertz.
For example, the vibrations of the human voice can vary between 300-4000 hertz. We hear sounds above 20,000 hertz worse. And fluctuations below 60 hertz are perceived by us as vibrations. High frequencies are called ultrasound, low frequencies are called infrasound.
Not all people respond the same way to different sound frequencies. This depends on many individual factors: age, gender, heredity, the presence of hearing pathologies, etc. Thus, it is known that there are people capable of perceiving high-frequency sounds - up to 22 kilohertz and higher. At the same time, animals can sometimes hear acoustic vibrations in a range inaccessible to humans: bats use ultrasound for echolocation during flight, and whales and elephants presumably communicate with each other using infrasonic vibrations.
At the beginning of 2011, Israeli scientists found that in the human brain there are special groups of neurons that allow one to estimate the pitch of a sound down to 0.1 tones. Most animal species, with the exception of bats, do not have such “devices”. With age, due to changes in the inner ear, people begin to perceive high frequencies worse and develop sensorineural hearing loss.
