Hearing faculty testing and apparatus therefor

• US 4,374,526 A
• Filed: 10/10/1979
• Issued: 02/22/1983
• Est. Priority Date: 02/10/1978
• Status: Expired due to Term

• Current Assignee: Otodynamics, Ltd.
• Original Assignee: National Research Development Corporation
• Inventors: Kemp, David T.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US06/230,957
• Time in Patent Office: 1,231 Days
• Field of Search: 128/746, 73/585, 73/589, 179/1 N
• US Class Current: 600/559
• CPC Class Codes: A61B 5/12 Audiometering
• CPC Class Codes: A61B 5/126 measuring compliance or mechanical impedance of the tympanic membrane
• CPC Class Codes: A61B 5/6817 Ear canal

Abstract

A hearing faculty test and apparatus therefor is based on the findng that sound input to the ear gives rise to a returned wave from and related to the condition of the inner ear, this wave being detectable as an echo from the ear drum. The apparatus preferably comprises a sealing aural probe (1) housing transducers (2,3) respectively to project a repetitive transient sound by pulse generator (4) activation and to pick-up for detection (5) successive echoes by time-gating. Detected echoes are preferably averaged during processing (6) for display. The echo occurs about 5-20 ms after its sound and a maximum operating frequency of about 50 Hz is appropriate. A continuous sound input can be used with consequent echo interference detectable as rapid changes of acoustic impedance with sound input frequency. Another alternative can involve detection of the ear drum movement by returned waves.

Claims

1. Hearing faculty apparatus comprising:

an aural probe for insertion in the external canal of a subject'"'"'s ear,

an electroacoustic transducer detector mounted in said probe to generate signals in response to sound pressure waves returned through said canal by reflection within the associated inner ear and reaction elsewhere, and

signal separation means connected with said transducer to extract, for retention from said signals, components thereof representing substantially exclusively only said inner ear reflection.

2. Apparatus according to claim 1 characterised in that said probe is formed to sealingly penetrate said canal.

3. Apparatus according to claim 2 characterised in that said probe includes a base part housing said transducer, and a replaceable part to engage said canal.

4. Apparatus according to claim 1, 2 or 3 wherein said sound source includes a pulse generator and a further electroacoustic transducer mounted in said probe and responsive to said generator to produce a repetitive transient sound.

5. Apparatus according to claim 4 wherein said signal separation means includes a time gate controlled by said generator to extract for retention from said signals only components occurring during a period from 5-20 ms following termination of each said sound.

6. Apparatus according to claim 4 characterized in that said generator is operable at a frequency not greater than about 50 Hz.

7. Apparatus according to claim 4 characterised by an averager responsive to the output of said separation means to average said retained components.

8. Hearing faculty testing apparatus comprising:

an aural probe for insertion in a subject'"'"'s external ear canal,

electroacoustic transducer means mounted in said probe for projecting sound into said canal and for responding to reactions produced by said sound in said canal,

a pulse generator for repeatedly activating said transducer means to project a sequence of transient sounds,

time-gating means responsive to both said generator and said transducer means for detecting delayed reactions produced by said sounds only within a period of from 5 to 20 ms following termination thereof to detect the reactions produced exclusively by return of said sound from within the inner ear of said subject, and

analyser means responsive to said detecting means for processing the detected echo signals at least by averaging a sequence thereof.

9. Hearing faculty testing apparatus comprising:

an aural probe for insertion in a subject'"'"'s external ear canal,

electroacoustic transducer means mounted in said probe for projecting sound into said canal and for responding to reactions produced by said sound in said canal,

a pulse generator for repeatedly activating said transducer means to project a sequence of transient sounds,

time-gating means responsive to both said generator and said transducer means for detecting delayed reactions produced by said sounds following termination thereof,

said time-gating means being constructed to detect the reactions produced by return of said sounds from within the subject'"'"'s inner ear substantially only during a period from 5-20 ms, and

analyser means responsive to said detecting means for processing the detected reaction signals at least by averaging a sequence thereof.

10. A method of testing hearing faculty comprising:

applying a sound to a subject'"'"'s ear,

detecting in electrical signal form the waves returned from the ear in response to said sound by reflection from the inner ear and other reactions, and

extracting for retention from said detected electrical signals components thereof representing substantially exclusively only said inner ear reflection.

11. A method according to claim 10 wherein said sound is of repetitive pulse form, and said extraction involves time-gating during a period following termination of each said pulse.

12. A method according to claim 10 wherein said sound is of continuous swept-frequency form and said extraction involves detection of interference between said components for retention and other signal components.