The normal Doppler effect causes sound waves to get longer if the source of the sound is moving away—for example, a receding ambulance siren.
The normal Doppler effect causes sound waves to get longer if the source of the sound is moving away—for example, a receding ambulance siren.
如果音源正在远离，平常的都卜勒效应会导致声波的波长变长──比如说，远离中救护车的警笛声，就是个很好的例子。