pitch of signal note

例句：

1. 1. The pitch of the song is so high that it can't be heard by most people.
   这首歌的音调太高了，大多数的人听不见。
2. 2. The pitch of the instrument was perfect for the music.
   乐器的音调非常适合音乐。
3. 3. The pitch of the voice changed as she spoke.
   当她说话时，声音的音调发生了变化。