3.10.2.2
Sensitivity and frequency response of the ear
Medical Physics | AQA A-Level Physics
- The auditory canal acts as a closed-tube resonatorA tube closed at one end (the eardrum) that resonates at a fundamental frequency determined by its length. For a 25 mm canal, the resonant frequency is around 3000-3500 Hz.. A tube of length $L$ closed at one end has a fundamental resonant frequency $f = \frac{v}{4L}$, where $v$ is the speed of sound. For a 25 mm canal, this gives roughly 3000-3500 Hz.
- The ear is most sensitive around 3000 Hz because of this resonance. Sensitivity drops off at both low and high frequencies.
- The human ear can detect frequencies from about 20 Hz to 20,000 Hz.
- The threshold of hearing is the minimum intensity the ear can detect, typically $I_0 = 1 \times 10^{-12}$ W m$^{-2}$ at 1 kHz.