Kazutoshi Mizoi

Wireless transmitting and receiving systems including ear microphones

A wireless transmitting and receiving system includes an ear microphone of the vibration pick-up type for picking up bone-conducted voice signals through an external auditory ear canal wall of a wearer. A portable case is disposed adjacent the wearers ear and a wireless device is attached adjacent the wearer but spaced from the portable case. A transmitter of a transmitting circuit for transmitting the output signals of the ear microphone is housed in the portable case. A receiver of a receiving circuit is housed in the wireless device and receives signals from outside the system. The transmitting and receiving circuits provide a wireless connection between the portable case and the wireless device permitting two-way communication through one ear of the wearer.

The Development of a Fibre Optic Catheter Tip Pressure Transducer

There has been much discussion on the distortion of intracardiac pressure waveforms measured by catheter methods. Tip transducers, which can eliminate this waveform distortion, have several problems. There are manufacturing difficulties with the mechano-electric transducing element. The devices also do not remain stable over variations in temperature and with long term clinical use. Safety problems may also be experienced due to the direct connection between external electronic devices and the heart. In order to overcome these difficulties, the application of fibre optics to the measurement of intracardiac pressure has been proposed. In this paper, the design, construction, and evaluation of a side-hole optic catheter, intended for intracardiac pressure measurement, is described.

Clinical Results of Hearing Aid with Noise-Level-Controlled Selective Amplification

We have developed a hearing aid which reduces the low-frequency energy of the input sound according to the input noise level and the spectrum of the environmental noise. The results of speech discrimination tests using speech in noise in 70 hearing-impaired subjects showed improvement in word discrimination scores in noise of over 15% for 50 of 53 subjects with sensorineural hearing loss. This group of hearing-impaired patients was subdivided into categories according to (a) audiogram type [flat, sloping (i.e. gradual high-frequency loss) and abruptly falling (steep high-frequency slope)]; (b) degree of hearing loss (less than or more than 50 dB average loss) and (c) etiology (familial deafness, presbyacusis). Results on 17 subjects with conductive or mixed hearing impairments showed no improvement, but expressed a preference for this system. The subject reported that the sound was more natural and quiet compared with the conventional AGC hearing aids.

Hearing aid for selecting voice sounds automatically using noisy environment

It is well known that one of the major complaints of a patient with a conventional hearing aid is low speech intelligibility due to the masking of speech by environmental noise. Consequently, a new hearing aid with selective amplification in the voice frequency band was developed using a compression amplifier which automatically compresses the lower frequency range as a function of the level and spectrum of the environment noise. This hearing aid consists of two filters and a compression amplifier. Sound signals from a microphone are divided by a low pass filter (LPF) and high pass filter (HPF). Only the sound signal passing through LPF is compressed with a compression amplifier and then mixed with the sound signal passing through HPF. In 40 dB ambient noise levels, this hearing aid shows flat frequency response. On the other hand, in environmental noises of more than 60 dB, the voice sounds become clearer and the S/N ratio of the voice sound is improved by selective compression of the lower frequency sou...