What are Assistive Listening Devices (ALDs) for TV, telephones, and theaters?
One of the major goals of signal processing schemes is to enhance the signal to noise ratio perceived by the listener. The use of aids with automatic low frequency reduction represent an attempt at this goal. Unfortunately, despite all the new technological advances, a basic problem remains for which wearable amplification falls woefully short. That problem relates to the physical distance between the microphone of the hearing aid and the source of the sound desired to be heard. Intensity (loudness) decreases as physical distance increases. Unfortunately most background noise surrounds the listener, so while the intensity of the speech decreases with distance, the intensity of the noise may not. This is one reason why hearing aids transmit sound so well if the speaker talks directly into the microphone, but at longer, more realistic distances reception diminishes.
One of the major goals of signal processing schemes is to enhance the signal to noise ratio perceived by the listener. The use of hearing aids with automatic low frequency reduction represents an attempt at this goal. Unfortunately, despite all the new technological advances, a basic problem remains for which wearable amplification falls woefully short. That problem relates to the physical distance between the microphone of the hearing aid and the source of the sound signal. Intensity (loudness) decreases as physical distance increases. Unfortunately most background noise surrounds the listener, so while the intensity of the speech decreases with distance, the intensity of the noise may not. This is one reason why hearing aids transmit sound so well if the speaker talks directly into the microphone, but at longer, more realistic distances reception diminishes. It would be ideal to have the sound produced at the source transferred directly to the listener without losing any intensity. I
