Beltone 12D Audiometer

© Brooke Clarke 2013

Background
As Received
Operation
Photos
Patents
Related
Theory
Links


Background

These audiometers (Wiki) were used for hearing tests, typically as a screening test in schools, but also other uses.  They make use of headphones where the left and right earpieces are wired to a separate jack so each ear can be tested individually.  The instrument has calibrated amplitude levels.

This is related to my other audio equipment, especially the General Radio Sound Level measuring instruments.

As Received

The pots are noisy and so the unit needs to be opened up and lubed with contact cleaner.

Operation

There is a provision to use either the supplied headset or a bone conduction headset.

There is also a provision to use a microphone or phonograph as an input source.  The front panel Speech meter & Switch seems to be for use with the external input sources and the switch beside it has three positions: P: Phonograph, M: Mike or Monitor?, T: Tape?  Let me know

When the TONE switch is set to Norm Off the unit only outputs tone when the space bar is pressed.  In the Norm On position there is tone present unless the space bar is pressed.

There are three positions of the OUTPUT switch: Bone, Right and Left.

The MASKING control can be OFF or set to a level.  It supplies noise to the ear that is not selected by the OUTPUT switch.  For example if you're testing the right ear with tone, the masking is in the left ear.

The left INTENSITY DB dial sets the hearing test level and is think should be calibrated.

The right FREQUENCY Hz switch allows selecting: SPEECH, 125, 250, 500, 750, 1000, 1500, 2000, 3000, 4000, 6000 or 8000 Hz tones.

The OFF-Gain & concentric Monitor knobs allow turning the unit on and off, not sure with gain and monitor do.  Let me know

The space bar at the front center turns the output either on or off depending on the TONE switch.

Photos

Fig 1
Beltone 12D
                  Audiometer
Fig 2
Beltone 12D
                  Audiometer
Fig 3
Beltone 12D
                  Audiometer
Fig 4
Beltone 12D
                  Audiometer
Fig 5
Beltone 12D
                  Audiometer
Fig 6




Patents

Beltone makes hearing aids so that's the subject of their patents., different OCR error name

Related

Audio Audio Connectors & Military Cloning - Fill - Retransmission
FreqStd Frequency Standard, Audio
GRsound General Radio Sound Measurement Instruments
HP204 HP 204B Audio Oscillator from HP 3350 Carrier Test Set (AN/USM-181 Telephone Test Set
HP241A HP 241A Audio Oscillator w/Radio Buttons
MAA Military Audio Accessories
PatchP Audio Patch Panel
SDAR Signal Design, Inc. 65630 Audio Recorder RD-609/TSQ-164 Communications Recorder
TS585 TS-585 Audio Level Meter
U229AA U-229 Audio Accessories
U229PO U-229 Pin Out by Function
U229Y "Y" Cable,  U-229/U

Theory

2016 - After reading an article about a new headphone that automatically matches it's frequency response to each of your ears and can recognize your ears (bio metric applications) I looked for more information.
Gizmag -Interview with the inventor: Nura's adaptive headphones turn our understanding of hearing on its head - Kiskstarter -
otoacoustic
emission (OAE) (Wiki) "
a sound which is generated from within the inner ear."

University of Melbourne - Luke Campbell - For your ears only -
http://www.nuraloop.com/ - June 2016 jumps to Kickstarter - Hardware Accelerator -

Historical Patents (no Nuraloop patents as of June 2016)

5792073 System and method for acoustic response measurement in the ear canal, Boys Town National Research Hospital, Aug 11, 1998, 600/559, 73/585

Uses two sound sources and time delays to cancel the fundamental reflected sound allowing fainter sounds to be detected.

Calls:

3294193 Acoustic impedance measuring instrument, Jozef J. Zwislocki, Dec 27, 1966, 73/585, 600/559, 600/200, 73/589, 73/645
Zwislocki (Pub Med), “Acoustic Measurement of the Middle Ear Function” (vol. 70 “Annals of Otology, Rhinology and Laryngology,” page 599 (1961) )
This is a mechanical system depending on balancing a bridge by varying the acoustic impedance of one side of the bridge.

Calls:
1784830 Mechanical impedance device, Bell Labs, Aug 25, 1928, 181/166 - related to measuring microphones & speakers like the GR Sound Measuring instruments
Used to measure microphones and speakers, like those in telephone handsets.
4374526 Hearing faculty testing and apparatus therefor, National Research Development Corporation,Feb 10, 1978, 600/559, 73/585 -  probe sealed to ear sends pulses and detects reflections

Links

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page created 5 March 2013.