fixed hearing aid

例句：

1. 1. He needs a new set of hearing aids to improve his hearing.
   他需要一副新的助听器来改善他的听力。
2. 2.The hearing aids are designed to help people with hearing loss.
   这些助听器旨在帮助有听力损失的人。
3. 3. The old man was very grateful for the fixed hearing aids that helped him hear better.
   这位老人非常感激那些帮助他听得更好的固定式助听器。