US 4,289,143 AGranted

Method of and apparatus for audiometrically determining the acoustic impedance of a human ear

AssigneeCSELT - Centro Studi e Laboratori Telecomunicazioni S.p.A.

InventorsFranco Canavesio, Rodolfo Ceruti

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Abstract

In order to determine the acoustic impedance of a human ear at various static pressures, a probe tightly fitted to the pinna of the ear transmits a short acoustic pulse with a wide frequency spectrum (such as white noise) from an electroacoustic transducer to the ear canal and receives back an acoustic response signal which a microphone converts into an electrical wave. The latter is digitized and transformed into terms of a Fourier series fed to a processor which, on the basis of similar terms stored in a memory and previously obtained with the same probe fitted to two different cylindrical calibrating cavities, derives therefrom the acoustic ear impedance at a particular air pressure. The processor also triggers an electric pulse generator, working into the electroacoustic transducer, and may progressively adjust a generator of static air pressure connected to the probe.

Claims7

Dependent claims

A method of determining the acoustic impedance of a human ear, comprising the steps of:

(a) tightly fitting a channeled probe to a first cylindrical calibrating cavity of radius a.sub.1 and a length L.sub.1 ;
(b) placing said cavity, via a channel of said probe, under a predetermined static air pressure P.sub.i ;
(c) transmitting to said cavity, via a channel of said probe, a short acoustic pulse encompassing a wide spectrum of audible frequencies;
(d) receiving back from said cavity, via another channel of said probe, an acoustic response signal and transforming an electrical wave converted into terms of a Fourier series representing a first set of amplitude samples S.sub.1i (.omega..sub.x) of a plurality of constituent frequencies f.sub.x =.omega..sub.x /2.pi.;
(e) storing the amplitude samples S.sub.1i (.omega..sub.x) obtained in step (d);
(f) repeating steps (a) through (e) with said probe fitted to a second cylindrical calibrating cavity of radius a.sub.2 and length L.sub.2, thereby obtaining and storing a second set of amplitude samples S.sub.2i (.omega..sub.x);
(g) repeating steps (a) through (d) with said probe fitted to the pinna of a human ear to be tested, thereby detecting a third set of amplitude samples S.sub.xi (.omega..sub.x);
and
(h) calculating the acoustic impedance Z.sub.xi (.omega..sub.x) for said air pressure P.sub.i and for different frequencies f.sub.x from the corresponding stored amplitude samples S.sub.1i (.omega..sub.x), S.sub.2i (.omega..sub.x), the corresponding detected amplitude samples S.sub.xi (.omega..sub.x), the propagation speed v of sound in air, and a fixed parameter .gamma., according to the following formula:
##EQU3##

7 more elements

An apparatus for determining impedance of a human ear, comprising:

a probe adapted to be hermetically secured to the pinna of a human ear and provided with a plurality of throughgoing channels;
a source of static air pressure communicating with a channel of said probe;
an electroacoustic transducer connected to one of said channels;
a microphone connected to another of said channels;
a generator of short electric pulses encompassing a wide spectrum of audio frequencies, said generator having an output connected to said transducer;
signal-analyzing means connected to said microphone for receiving an electrical wave emitted thereby in response to a pulse fed from said generator to said transducer and deriving therefrom, with a given air pressure P.sub.i from said source, a first set of amplitude samples S.sub.1i (.omega..sub.x) of a plurality of constituent frequencies f.sub.x =.omega..sub.x /2.pi. upon a fitting of said probe to a first cylindrical calibrating cavity of radius a.sub.1 and length L.sub.1, a second set of amplitude samples S.sub.2i (.omega..sub.x) of the same constituent frequencies f.sub.x upon a fitting of said probe to a second cylindrical calibrating cavity of radius a.sub.2 and length L.sub.2, and a third set of amplitude samples S.sub.xi (.omega..sub.x) upon a fitting of said probe to an ear to be tested;
memory means connectable to said signal-analyzing means for storing said first and second sets of amplitude samples;
and
processing means connected to said analyzing means and to said memory means for calculating the acoustic impedance Z.sub.xi (.omega..sub.x) for said air pressure P.sub.i and for different frequencies f.sub.x from the corresponding amplitude samples S.sub.1i (.omega..sub.x), S.sub.2i (.omega..sub.x) and S.sub.xi (.omega..sub.x), the propagation speed v of sound in air, and a fixed parameter .gamma., according to the following formula:
##EQU4##

7 more elements

Dependencies are inferred from the claim text.