Question

Why can a hearing test show that your threshold of hearing is 0 at 250Hz , when Figure 17.37 implies that no one can hear such a frequency at less than 20dB?

Short answer

The zero reference is 0dB and it is marked as threshold hearing

Step-by-step solution

The threshold hearing

The diagram shows the frequency vs. intensity of sound heard by a human ear:

The shaded region represents the frequency versus intensity found in normal speech.

Explanation

The graph represents the listener’s hearing that lies above the zero, reference level of the logarithm scale. 0 dB is the indication of the corresponding level in an audiometer. Thus, the zero reference is 0dB and it is marked as threshold hearing.