The Bass Loss Problem in Auditorium Acoustics

The Bass Loss Problem

低音损失问题

When sound drops off according to the inverse square law, the sound further from the source is not only perceived as less loud but also as deficient in the bass frequencies. This is a natural result of the human hearing response as revealed by the equal loudness curves. There is a bass discrimination in the human hearing response for soft sounds.

当声音按照反平方定律衰减时，远离声源的声音不仅被感知为更不响，而且在低频段也显得不足。这是人类听觉响应的自然结果，如等响度曲线所揭示的那样。对于弱声，人类听觉响应中存在低频辨别能力。

The Bass Loss Problem

低音损失问题

When sound drops off according to the inverse square law, the sound further from the source is not only perceived as less loud but also as deficient in the bass frequencies. This is a result of bass discrimination in the human hearing response as revealed by the equal loudness curves.

当声音按照反平方定律衰减时，远离声源的声音不仅被感知为更不响，而且在低频段也显得不足。这是人类听觉响应中低频辨别能力的体现，如等响度曲线所揭示的那样。

You can see that both the low frequency sound and the high frequency sound drop by 20dB when the distance is increased by a factor of ten. But the equal loudness curves are crowded closer together for the extreme low frequency range because the ear progressively discriminates against those low frequencies. So a 20dB drop at 30Hz bridges three equal loudness curves while the 2000 Hz sound bridges only two. The result is that the 2000Hz sound is expected to be perceived as 10 phons louder than the low frequency sound, and by the rule of thumb for loudness, that is twice as loud.

你可以看到，当距离增加到原来的十倍时，低频声和高频声的声压级都下降了20dB。但是，在极低频范围内，等响曲线更加密集，因为人耳对这些低频声音的辨别能力逐渐减弱。因此，30Hz的20dB下降会跨越三条等响曲线，而2000Hz的20dB下降只跨越两条曲线。结果是，2000Hz的声音预计会被感知为比低频声音高10 phons，按照响度的粗略规则，那声音是两倍响亮。