|Fig 1 Overall Photo
||Fig 2 Patent 4009707 Fig 1
Earphones/speakers and Microphones are necessary parts of radios, hence some interest in them as well as measuring the properties of ears/mouths as well as headphones/microphones.
When flying in a plane without cabin pressurization the air pressure gets lower as the altitude gets higher. If you yawn, chew gum or "pop" your ears the pressure on each side of the ear's diaphragm gets equalized. But if for some reason that does not happen then at some altitude the eardrum will be stretched outward and you will have diminished or no hearing. In a similar manner deep sea divers would experience loss of hearing when the pressure forces the eardrum in. Do skin divers loose their hearing when at some depth? Let me know.
The company that made this was Teledyne Avionics. I can see why a company that makes aircraft headphones would be concerned with the effects of air pressure on hearing.
1a: removable cover
1b: lower case
1c: AC Power Cord
3: Pressure Pump Control (+ or - pressure)
4: Presure Gauge
5: Compliance value in cc
6: Delta Compliance when (7) pressed
7: Stimulus Button
8: Stimulus Frequency
9: Stimulus Attenuator
10a: Compliance Standard 1
10b: Compliance Standard 2
11a: Compliance Cal 1
11b: Compliance Cal 2
12: Headset electrical jack
13: Headset perssure jack
14: Probe 220 Hz Tone On/Off (for audiometer use)
15: Earphone (works with 7, 8 & 9)
16: Pressure Transducer
17: Ear Probe
18: Ear Tip (choose size to fit)
From the on line papers I've seen the impedance is normally plotted from -200 to to +200 mm H2O pressure. The gauge on this unit measures between -500 and +250.
The calibration ports (Fig 4 below) are on the left side, not the front as in the patent drawing. They have volumes of 5.00 and 0.20 cc.
Fig 2 Patent 4009707 Fig 1
Fig 4 5.00cc and 0.20 cc calibration volumes
Fig 5 Rear panel
3294193 Acoustic impedance measuring instrument, Jozef J. Zwislocki, Dec 27, 1966, 73/585, 600/559, 600/200, 73/589, 73/645 - early mechanical acoustic impedance of ear
4374526 Hearing faculty testing and apparatus therefor, David T. Kemp, National Research Development Corporation, Feb 22, 1983, 600/559, 73/585 - detecting echos
4009707 Automatic acoustic impedance meter, John W. Ward, Teledyne Avionics, A Division Of Teledyne Industries Inc., Mar 1, 1977, 600/559, 73/645 - TA-3D
5738633 Oto-acoustic emission analyser, Christian Christiansen, Madsen Electronics A/S, Apr 14, 1998, 600/559 - Oto-acousticemission (Wiki) noise coming from the ear - can be used to test newborns inner ear function
Audio Audio Connectors & Military Cloning - Fill - Retransmission
Beltone 12D Audiometer
FreqStd Frequency Standard, Audio
GRsound General Radio Sound Measurement Instruments
HP 204B Audio Oscillator from HP 3350 Carrier Test Set (AN/USM-181 Telephone Test Set
HP241A Audio Oscillator w/Radio Buttons
HP 33120A 15 MHz Function/Arbitrary Waveform Generator goes way below audio
MAA Military Audio Accessories
SDAR Signal Design, Inc. 65630 Audio Recorder RD-609/TSQ-164 Communications Recorder
TS-2839/GY German Audio Test Set for UG77 military audio accessories
U229AA Audio Accessories
phones - Telephone patents + devices
TS-585 Audio Level Meter
HP 4395A Network, Spectrum & Impedance Analyzer
A closely related subject is Otoacoustic emission (Wiki). This relates to noises coming out of the ear. Not at all the same as an ear microphone where you use the ear to pickup the sound coming out of your mouth.
See patents above. This unit has some of the features for oto-acoustic emission testing, but is a little short of what's needed.
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