US3271520A

US3271520A - Acoustic reflex ear protective system

Info

Publication number: US3271520A
Application number: US242337A
Authority: US
Inventors: John L Fletcher; Arthur J Riopelle
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-12-04
Filing date: 1962-12-04
Publication date: 1966-09-06
Anticipated expiration: 1983-09-06

Description

Sept 69 1966 J. L. mama-2ER HAL L@ ACOUSTIC REFLEX EAR PROTECTVE SYSTEM J5 Sheets-Sheet l Filed Dec. 4, 1962 \N\/ENTO25 JOHN L.. FLETCHER AQTH Q .QwPELLE.

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ATTcaNE/ Sept- 5, 1966 @L L. FLETCHER mmm 39271952@ ACOUSTIC REFLEX EAR PROTECTIVE SYSTEM Filed Dec. 4, 1962 5 Sheets-Sheet B /e l N/ *.l

5/ a/ Il os@ LLA-V02 3/) AAA vv BY (mab/Mb ATTO @may United States Patent O 3,271 520 ACOUSTIC REFLEX EAR? PROTECTIVE SYSTEM John L. Fletcher, Fayettevilie, Arlt., and Arthur J. Riopelle, Orange Parli, Fla., assignors to the United States of America as represented by the Secretary of the Army Filed Dee. 4, 1962, Ser. No. 242,337 1 Clmm. (Cl. 179-1) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This application is a continuation-in-part to application Serial No. 67,443, filed November 4, 1960, now Patent No. 3,068,319.

The present invention relates to an acoustic reflex ear protective system and more particularly to an acoustic reflex ear protective system for introduction of a sound to the ear anticipatory to the reception of a second sound to the ear such that the ear is protected from noise-induced hearing ioss.

The introduction of a sound at the level of 80 to 110 decibels, for example, into the human ear causes a brief contracture of the stapedius and tensor tympani muscles of the middle ear and tightens the eardrum. The tightened eardrum is less free to vibrate and thus less able to transmit sound vibrations to the fluids of the inner ear. This contracture is termed the acoustic reflex.

A system exemplary of the present invention may include a source of energy, a pair of energy paths connected in parallel to the source, sonic generator means connected to each path and actuated by the energy source, and energy impeding means positioned in one path between the sonic generator means and the energy source such that actuation of one sonic generator means precedes actuation of the other sonic generator means by the energy source whereupon the sound produced by the first-actuated sonic generator means conditions by acoustic reflex the ear for reception of the sound produced by the lastactuated sonic generator means.

A second example of this invention comprises the programmed introduction of continuous protective sound or continual protective sound stimuli in situations where there is no control over the distressing sound.

An object of the present invention is to provide a new and improved acoustic reflex ear protective system.

Another object is the provision of an ear protective system to induce a sound to the ear to actuate acoustic reflex in advance of the reception of sound which otherwise could cause noise-induced hearing loss.

Still another object of this invention is to provide a system including circuitry adapted for use with standard military equipment.

A further object of part of this invention is the provision of an ear protective system which causes delay of the production of a deafening noise until after the production of a sound capable of conditioning by acoustic refiex the ear for reception of the deafening noise.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIG. 1 is a block diagram of the general concept of one embodiment of the invention;

FIG. 2 illustrates in schematic circuitry a portion of the embodiment of FIG. 1 disconnected from an input section of an audio frequency amplifier;

FIG. 3 is a view of the specific circuitry of the input section of an audio frequency amplifier of the embodiment 3,271,520 Patented Sept.` 6, 1966 lCC of FIG. 1, connected with the output of an oscillator section of the system;

FIG. 4 is a block diagram of a further embodiment of the invention for producing a programmed, continuous noise; and

FIG. 5 is a block diagram showing a modification of the embodiment of FIG. 4 including means for modulating the'programmed, continuous noise.

The first embodiment, illustrated in FIGS. l3 is i1- lustrative of an ear protective system wherein. control of the distressing sound is maintained.

Referring to FIG. 1 there is shown a voltage supply 11 connected to a firing trigger or switch 12 which is in series with a delay section 13 of the protective system. The output of the delay section 13 is fed to a tiring solenoid 14, which, when energized upon closing of the switch 12, actuates by mechanical linkage not shown, the firing mechanism of a gun 15, for example.

An oscillator section 20 illustrated in FIG. 1 is connected in parallel with the delay section 13 to the switch 12, as best shown in FIG. 3, with an output terminal 17 connected to the input point 18 of an audio frequency amplifier and mixer 19, FIG. l. The amplifier and mixer 19 is identified as AM-65/ GRC by the U.S. Army, and is described in detail in Technical Manual 1l-5039, an Army Signal Corps publication available from the U.S. Army Publications Branch, Office of The Adjutant General, the Pentagon, Washington 25, D.C.

Basically, the audio frequency amplifier and electronic mixer 19 includes three `channels 21 and is designed to provide interphone operation `and radio monitoring in installations using one or two receiver-transmitters and one or more interphone control boxes. The installation shown in FIG. l includes, for example, a radio receivertransmitter 22, designated by the U.S. Army as RT- 70/GRC, which is used for radio and interphone operation. The radio receiver-transmitter output is fed to input 23 of the amplifier and mixer 19. Input 24 of the amplifier and mixer 19 is used for a radio receiver and interphone, generally designated as numeral 25. Input 26 is available for intercommunication only between local stations, and has a parallel connection which serves as the input point 18 from the oscillator section 16. Control boxes 27 are selectively connected by three-position switches 28 to output channels 21 of the amplifier and mixer 19 and are in turn serially connected to headsets 31. The control boxes 27 are identified as C-375/VRC by the U.S. Army in TM 11-5039, referred to hereinabove.

As shown best in FIG. 2, the oscillator section 16 of the ear protective `system includes the output terminal 17 connected to an output volume control 29 of an oscillator 31, FIG. 3. A relay 32 with pairs of

contacts

33 and 34 has its actuating coil 35 operatively connected to the voltage supply 11 at terminals 36 by the trigger or switch 12. The relay 32 is actuated to close contacts 33 to complete a circuit from the oscillator 31 to an input section 37 of the audio frequency amplifier 19. Also, actuation of the relay 32 closes the contacts 34 to complete a circuit from the supply 11 to ground through a relay 38 which in turn closes contacts 39 to complete the connection between the oscillator 31 and the `audio amplifier 19.

The oscillator 31, FIG. 3, is a conventional R.C. coupled transistor oscillator, and, in the preferred embodiment of the invention, is designed with an output of approximately one volt at 1000 cycles per second. The oscillator 31 is powered by a 22.5 volt battery 41, for eX- ample, with the oscillator output appearing at terminal 17, which is connected through the output volume control 29 to the input point 1S of the amplifier 19.

A circuit for energizing the solenoid 14 is shown in FIG, 3 to include relays 42 and 43 in series arrangement having pairs of contacts 44 and 45 with coils 46 and 47, respectively. The relays 42 and 43 connect the solenoid 14 with the switch 12 and the voltage .supply 11, and are in parallel with the relay 32. A charging capacitor 48 and a variable resistor 49 are provided for delaying the actuation of the solenoid 14 by the source 11.

Cannon sockets 51 are utilized in the schematic views of the system in FIGS. 2 and 3 as terminal blocks.

The operation of the first embodiment is initiated by the firing trigger 12, which may be a hand gripped electrical switch, is closed by an operator whereupon 24 volts, for example, are applied from the voltage supply 11 to the charging capacitor 48 and the variable resistor 49. The current sensitive relay 42 has its coil 46 energized upon charging of the 100 microfarads, capacitor 48 for example, at which time the contacts 44 of the relay 42 complete the circuit for energizing the relay 43. Through the closing of the contacts 45 of the relay 43, the 24-volt circuit is completed to the solenoid 14, causing a gun 15, for example, to fire.

Also, when the firing trigger 12 is closed, 24 volts from the supply 11 are applied to the relay 32, energizing the coil 35 and causing the two ysets of

contacts

33 and 34 to close. The closing of contacts 34 energizes the relay 38 in the input section 16 of the amplifier 19 to complete an input circuit, and the closing of contacts 33 completes the circuit from the output terminal 17 of the oscillator 31 to the input point 18 of the amplifier 19. The output of the amplifier 19 is distributed to one or more of the control boxes 27 and is then fed into earphones 31 worn by an operator to cause an acoustic refiex in his ears. The delay in the firing circuit caused by the charging capacitor 48 is sufficient to permit reception of the output signal from the amplifier 19 into the ear of an operator through headsets 31 prior to the energization of the solenoid 14 which causes a gun 15 to fire, for example. Accordingly, the ears of the operator are protected from the damaging effect of the gun noise by activation of the acoustic reflex by the output of amplifier 19 in advance of the firing of the gun.

The second embodiment of which FIGS. 4 and 5 are species provides for protection against continuous distressing noise or continuous protection against noncontinuous distressing noise over which control is not maintained.

In the species of FIG. 4, the acoustic reflex is activated and maintained in its activation by cycle per second pulses or clicks These pulses are generated by a multivibrator and amplified by an audio amplifier with a good low frequency response and fed into earphones or speakers. Research has shown that pulses at 15 c.p.s. at a proper sound pressure level at the ear of about 105 db re .0002 dyne/cm.2 will activate the reflex `and keep it contracted. Although the reflex sound decreases hearing due to exposure to background noise, the hearing is not otherwise affected by the sound. In the species of FIG. 5, a ring modulator acting in combination with a signal generator and the 15 c.p.s. pulses from the multivibrator enable an audio amplifier of inadequate low frequency response to be used in the system. If the audio amplifier can faithfully reproduce the 15 c.p.s. pulses, the ring modulator and the signal generator may, of course, be eliminated. In this system, unlike the first embodiment (FIGS. 1-3) the sound producer (multivibrator) is turned on manually before exposure to the noise for which protection is desired, left on as long as the noise persists, and turned off manually when the noise exposure is terminated. It does not include control of the source of the hazardous noise.

The above-mentioned components are well known to those skilled in the art and are commercially available. No Ispecification or limitations other than mentioned above are required.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. For example, the relay 43 may be omitted if the contacts 44 of the relay 42 are capable of carrying the 6 ampere current, in the preferred embodiment, necessary to operate the firing solenoid 14. Similarly, the audio amplifier 19 may be omitted from the ear protective system should the output power of the oscillator 31 be sufficient to deliver the acoustic energy required to create acoustic refiex in the human ear. It is therefore to be understood, that within the scope of the teachings herein, the invention may be practiced otherwise than as specifically described.

We claim:

Apparatus for producing continuous sound for placing the ear in acoustic reflex condition for continuous protection against distressing noise comprising:

(a) a multivibrator continuously producing pulses at the rate of l5 cycles per second;

(b) a signal generator;

(c) a ring modulator electrically connected to said signal generator and said multivibrator;

(d) an audio amplifier electrically connected to said ring modulator; and

(e) a speaker electrically connected to said audio amplifier, said speaker impressing the continuous 15 cycle per second pulses upon the ear thereby producing the acoustic reflex condition.

References Cited by the Examiner UNITED STATES PATENTS 10/1956 Konrad 340-384 12/1962 Fletcher et al. l79--l.8