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Impedance Audiometer

Toronto Rehabilitation Institute · Health Sciences

An electronic instrument with wood grain paterned sides, dull green coloured top and lower-front surfaces, and a slanted metallic console. The console has two centrally-positioned rectangular dials, as well as several knobs, buttons, and switches.

Attached to jacks at the back of the instrument is a “headset and transducer” assembly consisting of a headphone one earpieces, and a separate pneumatic probe terminating in a narrow metal ear probe. The headphone is labeled “Telephonics” and “TELEX”.

A grey-coloured power cable is also attached to the back of the instrument.

A substantial “Operation Manual” was acquired with the object.

Accession Number:

Alternative Name: Impedance Audiometer AZ7

Primary Materials: Iron alloy, Plastic, Aluminum alloy.


A cue card placed on the top of the instrument reads: “BRIDGE// Leave on “audiometry” when not in use// Switch to “Compliance” for testing// Pump should be “up”// Turn dial slowly to +200 & see compliance// Reading on L side of machine – bring pump slowly towards 0 & see peak E Compliance reading on L – Subtract to get values”
The reverse side of the card reads: “Audiometry – Stimulus presented through headphone 226Hz none on the opposite side.”
An embossed label on the top surface reads “EMI// electro-medical instrument co. Oakville, Ontario.”
Two EMI calibration labels contain the following information:
“Dec/2/2010 // Recal Dec 2011” and “Pump Tube Nov/02/09 // Recal Nov 2010”

A sticker on the rear surface of the instrument reads: “Pump Tube Replaced Feb 96”

A sticker on the left side of the instrument reads: “The Queen Elizabeth Asset No. 20462”

A “Special Inspection Service” sticker from the Canadian Standards Association contains the following information “Model: A27″, Serial:5943”.

The “TELEX/ Telephonics” headphone includes the following numbers: “TDH-39P”, “60257”, “296D000-1”.

Dimensions (cm): Height = 12, Width = 34, Length = 26.


The impedance audiometer is a medical diagnostic instrument that tests hearing acuity. It measures the flexibility of the eardrum by generating variable pressure within the ear canal.


Very good: There are some dark marks on the top surface of the artifact, as well as minor scuffs and marks across its surface.

Associated Instruments:

Manufacturer: Unknown

Date of Manufacture: Unknown


This artifact among a collection of items acquired from the Toronto Rehabilitation Institute on December 6th, 2017.

Additional Information and References:

Chapter 9 of the Operation Manual lists a number of relevant sources about Impedance Audiometry.

Historical Notes:


  • Donated to UTSIC