Check slabovidimym acoustic signals is of great practical importance. This: fault diagnosis of internal combustion engines; search for places of leakage of gas from the damaged pipeline networks; early detection of diseases of internal organs; organization of acoustic communication and alarm systems; capture seismography, noise of different origin, including sounds of nature (birds singing, for example) and many more.
Highly sensitive device for recording of weak acoustic signals (electronic ear) are shown in Fig. The device used a miniature electret microphone type MCE-333. The microphone body is connected to the common wire. The low-frequency amplifier implemented on the chip К237УН1 included in the scheme, close to the model. The device operates from a battery voltage of 6 V. When powered device from the rectifier is necessary to provide a minimum penetration of signal power frequency of power circuits increases capacitances C1, C2.
The resistor R4 is set according to the recommended for a particular instance of the chip value (resistance value in Kromah and the number of “legs” of the chip, between which and the common wire should be attached to the resistance, usually indicated on the chip). If the value of R4 is not specified, its value is selected experimentally (tens of ohms). The device is operating at supply voltages 3-9,8 In consumption and the current of 2-6 mA.
In Fig.2 shows a printed circuit Board. The sensitivity of the device is such that even without additional zvukoizoliruyuschie the mouthpiece this electronic ear registers a confident whisper from a distance of up to 5 m, street noises — above 100 m. the efficiency of the device can be significantly improved by the use of acoustic reflectors and lenses. As a hub of acoustic radiation can be used for automobile and other headlights (no glass); searchlight horn and corner reflectors; reflectors; parabolic antenna; natural and artificial cavities; cavities and areas of focus to be placed on the microphone. Because the microphone MKE-333 is not directed, it is desirable to provide an acoustic shielding with the use of a eat the sound-absorbing material (e.g. foam rubber). The efficiency of the device increases in proportion to the ratio of the areas involved in the conversion of acoustic energy (the source area of close to 1 cm2). The device can be used to prevent cave-ins in mines: as subsidence of the layers significantly enhanced the cracking of destructible rocks, and a sharp increase in the intensity of acoustic signals indicate the approach of the collapse of the layers. In medical diagnostics the device may be used to detect natural sources of biological noise are: beating of heart, rattling in lungs, sounds of Korotkoff, etc. Especially promising is the use of two-channel (stereo) versions of the device, allowing you to create a consistent picture of the processes occurring in the human body. For greater objectivity of the recorded acoustic parameters of the signal from the microphone sensors can be entered into a computer, where software enhanced surround creates a dynamic picture of the processes occurring in the body (acoustic tomography). The device can also be used for diagnostics of technical devices (noises in engines, gear boxes, etc.); it is desirable to include the smooth changes in gain.
A circuit diagram and a printed circuit Board, the self-made device (the electronic ear) for Express analysis of the state of the art and other objects, including biomedical
Electronic ear can be used for persons with impaired hearing or vision. In the latter case, consistently with the telephone earpiece includes a second auxiliary fuse that is shared with the microphone in a cane box or other device. The microphone and earpiece should have highly directional diagram of the reception (radiation) due to the introduction of sound-insulating linings and casings. When approaching the obstacle in the device occurs positive acoustic feedback sound signal is generated, the height of which is determined by the distance from the device to the obstacle. At certain skill to operate similar electronic cane you can confidently determine the distance to the obstacle, its approximate size and even material.
“Electronic ear” can be used as an indicator of swarming bees; to organize the protection of various objects such as for detection of acoustic signals emitted by the violator and the termination (attenuation) of the acoustic signal from a sound emitter installed on the distance from the receiver sound. On the basis of the device may be arranged an acoustic connection between the subscribers (when using acoustic reflectors working both on reception and transmission in the focus of the reflectors should be located on the microphone and zvuchaschaya head). In order not to create acoustic interference others, the spectrum of the audio signal, it is desirable to move at 10-20 kHz (single sideband or frequency modulation).
The device can be used not for its intended purpose. When connecting instead of the electret microphone capsule or electromagnetic multiturn inductors is possible to register a variable magnetic field, the magnetic noise, the organization of the inductive coupling, the implementation of remote control systems, etc.
M. SHUSTOV, Tomsk