Telephone vs. Voice Over IP Speech Comprehension in Hearing Aided Subjects.

Speech comprehension of hearing impaired individuals is limited in telephone conversations due to the limited acoustic spectrum transmitted by conventional analogue telephones, such as background noise, interferences with the hearing aid and the absent possibility of lip-reading. This can provide an impact on quality of life as better speech comprehension reduces exclusion from social interactions as well as potential professional occupations. Furthermore, in elderly population an impaired hearing function is associated with a higher risk of dementia, mortality rate and dependency in the daily activities.

Mantokoudis et al. recently demonstrated that the larger acoustic spectrum of internet telephony (Voice over Internet Protocol [VoIP]) results in superior speech comprehension of individuals with hearing aids compared to conventional telephones. Low signal quality during internet telephony does not significantly attenuate speech understanding. Another study revealed that internet telephony combined with a webcam further improves speech comprehension as additional lip reading was possible.

New bluetooth audio streaming devices allow for pairing with smart phones or other devices supporting bluetooth technology such as computers for direct routing of the audio signal to the hearing aid. Current state of research shows significant benefits for hearing impaired individuals using this technology for telephone conversations. The speech comprehension and subjective satisfaction can be improved due to a better sound quality and accuracy and less noise interference.

However, speech comprehension of these new bluetooth devices has not been investigated in combination with internet telephony (VoIP) and it remains unclear whether hearing impaired individuals could benefit of this possibility. This study investigates, whether bluetooth audio streaming devices paired to hearing aids/implants combined with internet telephony improves speech comprehension in hearing impaired individuals.

VoIP and conventional telephone speech comprehension will be compared with and without a wireless bluetooth phone clip (Cochlear Wireless Phone Clip, Cochlear Ltd., 1 University Avenue, Macquarie University, New South Wales 2109, Australia). The phone clip is capable to directly connect to other bluetooth-enabled devices and transmits the audio signal directly to the sound processor of the hearing implant. A microphone in the phone clip enables to record and transmit the user's spoken words to the mobile phone therefore a hands-free use is possible.

Bluetooth connection is a well-established wireless technology transmitting at 2.4 gigahertz at distances up to approximately seven meters. The wireless technology is the same for most of bluetooth and Wireless Local Area Network (WLAN) devices. According to the Swiss federal health office the electromagnetic radiation of the bluetooth device as intended to be used in the proposed study fulfils the requirements of the European Committee for Electrotechnical Standardization (CENELEC).

Several previous studies demonstrated a significantly increased conventional telephone speech perception with the Cochlear Wireless Phone Clip than without this device. On the other hand, speech perception in hearing impaired people using internet telephony is improved compared to conventional telephony. However, speech perception using the phone clip in connection to internet telephony has not been studied to this date and remains unknown.

The purpose of the proposed study is to quantify VoIP vs. conventional telephone speech comprehension in individuals with or without application of bluetooth phone clip. Potentially better speech comprehension due to the application of the phone clip could alleviate the handicap of communication in individuals with hearing aids. As a consequence the social life and contacts of the affected individuals such as worsening of mental state and dependency in the everyday life could be ameliorated only by using a simple device.

The goal of this study is to measure speech comprehension of individuals with hearing aids using a bluetooth paired phone clip and VoIP telephony. To quantify a potential benefit of this, speech comprehension has to be tested with and without the phone clip for VoIP and conventional telephony in the same individuals. Speech comprehension will be quantified with a signal/noise ratio of the HSM- sentence test (Hochmair, Schulz, Moser)

Upon agreement to participate, patients are invited to the audiological department at Inselspital in Bern. After remaining questions are clarified, the patient has to sign a written informed consent. The investigation will take approximately two hours and takes place in the sound-proof hearing test chambers of the audiological department.

Four different speech comprehension scenarios are tested:

1. Conventional telephony without bluetooth device
2. Conventional telephony with bluetooth device
3. VoIP telephony without bluetooth device
4. VoIP telephony with bluetooth device

To evaluate speech comprehension, the HSM (Hochmair-Schulz-Moser) sentence test is used. This is a test mainly applied to evaluate the speech comprehension in patients with cochlear implants and consists of 30 lists each including 20 short sentences. After initial presentation of exercise sentences without background noise, additional noise is added while the speech signal is kept at a constant volume level. The percentage of speech comprehension is determined by the quantity of correctly understood sentences at a certain signal-to-noise ratio (S/N Ratio). In this study a S/N Ratio of 10dB, with a signal at 70dB and noise at 60dB, will be analysed.

For representativeness of speech comprehension results, participants will use their hearing aids with their daily use volume settings. The phone clip will be programmed for a 1:1 transmission of the telephone conversation and the ambient noise. At the end, the patient has to evaluate the subjective perception of the speech sound quality by means of the Mean Opinion Score (MOS).