Panasonic's new technology: Inferring the maximum volume of hearing aid users for brain waves

Panasonic has developed a technology that uses brain waves to infer the maximum volume suitable for hearing aid users. The company plans to launch it as a hearing aid volume automatic adjustment system in 2015.

Previously wearing hearing aids required "Fitting" to adjust the volume of each frequency of the hearing aid according to the user's hearing characteristics. The reason is that there are individual differences in the auditory characteristics of the hearing impaired, and the allowable upper volume limit is very different. Since the upper limit value was always obtained from a simple calculation based on the lower limit value obtained by auditory examination, the upper limit value includes an error due to individual differences. However, since the initial volume adjustment of the hearing aid needs to be performed using this upper limit value, the user will hear a discomforting sound, and it takes a long time to repeatedly adjust the volume to reach the optimal volume, causing a great burden on the user.

This new technology is mainly realized by two new technologies: (1) brainwave analysis technology and (2) best stimulation technology.

The brain wave analysis technique of (1) analyzes the brain wave change pattern when the user hears Panasonic's self-developed test tones (the pure sounds of different sizes that are issued multiple times within one second), thereby accurately estimating the allowable sound volume. Limit value. First, a test tone (consecutive test tone) was developed in which the volume of a pure tone at the same frequency was reduced by 5 dB in increments of 80 dB (the same level as the noise level in the interior of the train) and emitted three times at intervals of 300 ms.

In addition, the “wavelet analysis” (developing the brainwave pattern over the time-frequency range) of the electroencephalogram pattern when the hearing aid user hears the continuous test tone was found to have an individual difference due to the allowable volume upper limit value. There is a difference in the response intensity of hearing aid users to the second and third test tones. By the discrimination analysis of this reaction intensity, the allowable volume can be estimated with high accuracy (with an average error of ±5 dB or less).

The best stimulation technique of (2) changes the frequency of the test tone in order not to let the brain's response to the same stimulus. According to Panasonic, if the same frequency sound is repeated at short intervals, the brainwave pattern will change due to the habit of sound, and the error will increase. Therefore, the original brain wave measurement required stretching the interval between sounds to at least 1 second.

This time, we have prepared test frequencies for the four frequencies (500Hz, 1000Hz, 2000Hz, and 4000Hz) that are very important for listening to conversations. The frequency will be determined according to the principle that the same frequency will not appear continuously, and the test tone will be sent to either side Ears. Therefore, even if the interval between consecutive test sounds is set to about 500 ms, there is no habitual influence, and the estimation can be completed within a short period of time of about 5 minutes.

In order to verify the effectiveness of this technology, Panasonic launched a clinical evaluation of hearing aid users with the Fukui University Medical Department in November 2011.