Here is the Block Diagram for our system:

Why use digital hearing aids?

Approximately 10% of the world's population suffer from some type of hearing loss, yet only a small percentage of this statistic use a hearing aid The stigma associated with wearing a hearing aid, customer dissatisfaction with hearing aid performance, and the cost associated with a high performance solution are all causes of low market penetration.

Current analog hearing aids yield significant limitations due to their inadequate spectral shaping, narrow operating bandwidth, and only partial noise-reduction capability. This leads to sub-optimal clarity and audibility restoration, as well as sub-optimal speech perception in noisy environments. Analog hearing aids are hardware-driven and thus are difficult to customize to specific hearing problems.

Digital hearing aids can solve these problems. They provide full bandwidth, fine grain spectral shaping, and enhanced noise reduction. As software-driven devices, they are very flexible and easily customizable to a user's needs.

How does the digital hearing aid system work?

The analog sound signal is converted into digital domain. The digital signal processor at the heart of a digital hearing aid manipulates the signal without causing any distortion, so sounds come through more clearly and speech is easier to hear and understand. The DHP combines crisp digital sound with totally hands-free operation, making it a logical choice compared to many of the other, more traditional solutions available.

We made the following assumptions about our system:

· The highest frequency that most humans can hear is approximately 20 kHz. Therefore, before the signal enters the A/D converter, it will be lowpass-filtered to 20 kHz, which is also our sampling frequency. This will avoid aliasing during sampling.

· Our hearing aid will be behind-the-ear so we can avoid any effects of feedback, which may occur in a small inside-the-ear hearing aid where the microphone and speaker are very close to each other.

· It does not operate in real-time, since we take in the entire speech signal and then manipulate it.