feedback
このページの評価をお願いします

サポート情報をお探しですか?


イベント

Howling Hearing Aids: Improving User Control and Tuning Flexibility in Feedback Cancellation 

 著者: Jim Ryan - 2015-03-25 09:18:40.0

Feedback in hearing aids, the loud and annoying howling sound that can be heard by bystanders, has always been one of the most bothersome issues faced by hearing aid wearers. Back when hearing aids were made with analog integrated circuits, and even in the early days of digital, feedback had to be managed by lowering the overall gain of the hearing aid (limiting fit rates) or by adjusting the frequency response of the device by inserting a notch filter at the feedback frequency to reduce the gain in that area. Unfortunately, this had the detrimental effect of also lowering the gain in those frequencies of the sounds the hearing aid wear wanted to hear. 

Now, Adaptive Feedback Cancellation (AFC) has become a ubiquitous feature in digital hearing aids. AFC operates by subtracting an estimate of the hearing-aid feedback signal from the microphone signal. If the feedback estimate matches the actual feedback picked up by the microphone, the feedback is eliminated. This approach to feedback suppression is preferred over other methods because it actually eliminates feedback and permits an increase in gain compared to that possible without AFC.

Correct AFC operation depends on the internal estimate matching the actual feedback paths present in the hearing aid. Unfortunately, hearing-aid feedback paths are not constant. There is significant variability in the feedback paths of different hearing aids due to factors such as transducer selection, acoustic tubing, ear mold styles, etc. Furthermore, the feedback path of a specific hearing aid can also change with time due to user movements and environmental changes. If such changes are not reflected in the internal feedback path, then canceller performance will be significantly degraded.

To maintain optimal cancellation performance, AFC performs continuous adjustments of the internal feedback-path model. These adjustments occur automatically and utilize the existing hearing aid signals. No user intervention or special probe signals are required, thus minimizing disruption for the hearing-aid wearer.

To eliminate feedback quickly, fast AFC adjustments are required. Fast adjustments make large, rapid changes to the internal feedback model allowing feedback to be eliminated quickly. Unfortunately, fast adjustments can also lead to errors in the model resulting in audible distortion known as entrainment. Entrainment can be reduced with slow adjustments but eliminating feedback will require more time.

Previous AFC designs from ON Semiconductor represent a compromise between fast and slow adjustments. The compromise setting maintains excellent audio quality while allowing for quick feedback elimination. But, since user adjustments were not available, this did not represent the best choice for all situations.

The AFC algorithm provided in RHYTHM™ R3920 from ON Semiconductor solves this problem using a new gear-shifting mechanism that provides memory-specific adaptation-speed adjustments. This new feature allows faster feedback elimination with excellent audio quality and provides the flexibility to tune AFC behavior for wide range of conditions.

ON Semiconductor’s hearing health team will be on-site at the 2015 Audiology NOW! conference in San Antonio (March 25-27th). Stop by our booth (191) to speak with one of our many audio experts.

 

Tags:Digital Signal Processor, Medical

この記事の感想は?

0 0 0 0 0

コメントを投稿

Eメール・アドレスは公開されません。 *印は必須項目です

名前*

Eメール・アドレス *

コメント


以下に記載されたルールに従って投稿してください。ルールに反したコメントは削除される場合があります
  • 丁寧な言葉で、下品にならない、良識のある文章をお願いします
  • SPAM、広告・宣伝、いかなる種類の紹介販売プログラムの禁止
  • 他のユーザへの意図的かつ繰り返される攻撃の禁止
  • 荒らし・釣りなど、他のユーザへの意図的な敵対行為の禁止
  • 電話番号やEメール・アドレスなどの個人情報は記載しないでください。その結果によるいかなる望ましくない結果に対し、当社は責任を負いません。

コメント

Dave Thompson 2015-07-01 13:25:59.0 コメント・レーティング: Vote down 0 Vote up
It is cool how much hearing aids have gotten better over the years. They are being made smaller and with little to no feed back. I can't wait to see how hearing aids Evolve in the next few decades or so. http://www.thehearingspecialists.com/hearing-aids
Dave Thompson 2015-06-11 15:56:38.0 コメント・レーティング: Vote down 0 Vote up
It is very cool that hearing aids are getting better every year. I remember when my grandmother got her first pair of aids she said she could hear a bunch of static. Now when she tells me about them she tells me she sometimes forgets they are even in her ear they are so natural. Thanks for the great post on hearing aids. http://www.dunlophearingaidservice.ca/hearing_aids.html

「エキスパートに質問」ナリッジ・データベース
 
設計に関する質問と回答を参照、または新たな質問を投稿
 
 

読者登録
   
 

ツイッター・フィード