Method and apparatus for testing hearing ability
The present invention concerns a method for the detection of distortion products of otoacoustic emissions (DPOAE), comprising the steps: (a) output of at least one first pair of primary tones each consisting of a first primary tone with frequency f 1,1 and sound pressure level L 1,1 and a second primary tone with frequency f 2,1 and sound pressure level L 2,1 with f 2,1 >f 1,1 , and (b) detecting evoked distortion products of otoacoustic emissions (DPOAE), characterized in that the first primary tone {f 1,1 , L 1,1 } is output with a time delay t lag after the second primary tone {f 2,1 , L 2,1 }.
1. A method for detecting distortion products of otoacoustic emissions (DPOAE) in a hearing organ comprising the steps of:
(a) output of a first primary tone pair {f 1,1 , L 1,1 , f 2,1 , L 2,1 } each comprising a first primary tone with frequency f 1,1 and sound pressure level L 1,1 and a second primary tone with frequency f 2,1 and sound pressure level L 2,1 with f 2,1 >f 1,1 , and
(b) detection of evoked distortion products of otoacoustic emissions (DPOAE), wherein the first primary tone {f 1,1 , L 1,1 } is output with a time delay tag after the second primary tone {f 2,1 , L 2,1 },
wherein at least one further primary-tone pair is presented, consisting of a first primary tone with frequency f 1,n and sound pressure level L 1,n and a second primary tone with frequency f 2,n and sound pressure level L 2,n where f 2,n >f 1,n , wherein the second primary tone {f 2,n , L 2,n } of the at least one further n-th primary-tone pair has a time delay tag after the first primary tone {f 1,n , L 1,n } of this primary-tone pair,
wherein {f 1,1 , L 1,1 }={f 1,n , L 1,n } and {f 2,1 , L 2,1 }={f 2,n , L 2,n }, and
wherein the method further comprises a step of comparing the DPOAE evoked by output of the first primary-tone pair {f 1,1 , L 1,1 , f 2,1 , L 2,1 } with the DPOAE evoked by the output of each n-th further primary-tone pair {f 1,n , L 1,n , f 2,n , L 2,n }.
2. The method according to claim 1 , wherein the output of the at least one further n-th primary-tone pair {f 1,n , L 1,n , f 2,n , L 2,n } takes place before or after the output of the first primary-tone pair {f 1,1 , L 1,1 , f 2,1 , L 2,1 }.
3. The method according to claim 1 , where n=2.
4. The method according to claim 1 , wherein the first primary tone {f 1,1 , L 1,1 } and/or {f 1,n , L 1,n } (“f 1 -pulse”) and optionally the second primary tone {f 2,1 , L 2,1 } and/or {f 2,n , L 2,n } (“f 2 -pulse”) can be presented pulsed.
5. The method according to claim 4 , wherein a pulse length of the f 1 -pulse of the first primary-tone pair {f 1,1 , L 1,1 } is shorter than a pulse length of the f 2 -pulse of the first primary-tone pair {f 2,1 , L 2,1 }, and/or a pulse length of the f 2 -pulse of the n-th further primary-tone pair {f 2,n , L 2,n } is shorter than a pulse length of the f 1 -pulse of the n-th further primary tone pair {f 1,n , L 1,n }.
6. The method according to claim 4 , wherein the f 1 -pulse of the first primary-tone pair {f 1,1 , L 1,1 ; f 2,1 , L 2,1 } is switched off before or after the end of the f 2 -pulse of the first primary-tone pair.
7. The method according to claim 1 , wherein the time delay tag is between 10 ms and 0.1 ms or between 5 ms and 0.5 ms.
8. The method according claim 1 , wherein a duration of the f 1 -pulse of the first and optionally each further n-th primary-tone pair and/or a duration of the f 2 -pulse of the first and optionally each further n-th primary-tone pair is selected to be greater than a latency of the evoked DPOAE, or at least twice, or at least three times or at least five times as long.
9. The method according to claim 1 , wherein a duration of the first primary tone {f 1,1 , L 1,1 } of the first primary tone pair and/or of the second primary tone {f 2,n , L 2,n } of the n-th further primary-tone pair is 200 ms or less, 100 ms or less, 50 ms or less, between 40 ms to 1 ms, between 30 ms and 2 ms or between 25 ms and 5 ms.
10. The method according to claim 1 , wherein a set of the first primary-tone pair {f 1,1 , L 1,1 ; f 2,1 , L 2,1 } and the at least one further primary tone pair {f 1,n , L 1,n ; f 2,n , L 2,n } is output in a block which is repeated several times during a measurement period.
11. The method according to claim 10 , wherein in a block a beginning of a primary-tone pair follows a beginning of the primary-tone pair immediately preceding in the block with a time interval T a , where T a is >10 ms.
12. The method according to claim 10 , wherein in a block second excitation frequencies f 2 of two immediately successive pairs of primary tones are at least one octave apart.
13. The method according to claim 10 , wherein during the measurement period measured sound pressure levels of the DPOAE are averaged for primary-tone pairs of same second excitation frequencies f 2 .
14. The method according to claim 10 , wherein the or each block of primary-tone pairs is presented during a block time selected such that there is a time interval of 30 ms to 100 ms, or at least 70 ms, between a beginning of a first and a subsequent primary-tone pair with same excitation frequencies f 2 .
15. The method according to claim 10 , wherein sound pressure levels of the DPOAE are measured and averaged for all second excitation frequencies f 2 contained in a or each set at a second sound pressure level L 2 respectively associated with an excitation frequency f 2 , and measurements of sound pressure levels of the DPOAE are performed at least once for new sound pressure levels L 2 .
16. The method according to claim 1 , wherein a duration of the first and second primary tones of each pair of primary tones is between 2 ms and 20 ms.
17. The method according to claim 1 , wherein at a beginning of measurements it is checked whether a frequency f dp of one of the DPOAEs interferes with a spontaneous emission (SOAE).
18. The method according to claim 1 , further comprising automatically determining an individual function of a DPOAE level map having p dp,I =f(L 1 , L 2 ) to determine an optimal DPOAE excitation level:
Reading a model function p dp,M =f(L 1 , L 2 ) with model parameters of a DPOAE level chart, based on a number of N DPOAE measurements of an excitation frequency pair f 1 , f 2 each with different level pairs {L 1 (1 . . . N) , L 2 (1 . . . N) } in a population (p) of subjects with normal hearing, into a working memory of a computer unit, where N≥40 and p≥2,
automatic presentation of n different level pairs {L 1 (1 . . . n) , L 2 (1 . . . n) } of an excitation frequency pair f 1 , f 2 via sound output means to an individual and detecting a corresponding DPOAE of the individual via sound recording means, wherein at least a first level pair {L 1 (1) , L 2 (1) } is predefined and where n<<N,
iterative fitting of a model level-map function p dp,M =f(L 1 , L 2 ) to measured n DPOAE until an individual function is obtained p dp,I =f(L 1 , L 2 ) with individual parameters of a DPOAE level map of the individual by the computer unit,
output of the individual function p dp,I =f(L 1 , L 2 ) and/or their individual parameters on an output device of the computer unit.
19. The method according to claim 18 , wherein the model function has an approximately linearly increasing ridge ( 73 ) which is approximately linearly related to {L 1 (G) , L 2 (G) } level pairs, at least half of measured level pairs {L 1 , L 2 } being at least 5 dB on both sides away from the group of signals evoked by the level pairs {L 1 (G) , L 2 (G) } associated with the ridge ( 73 ).