Question

Based on the graph inFigure$\mathbf{17}.\mathbf{36}$, what is the threshold of hearing

in decibels for frequencies of$\mathbf{60},\mathbf{400},\mathbf{1000},\mathbf{4000},\mathbf{a}\mathbf{n}\mathbf{d}\mathbf{15},\mathbf{000}\mathbf{H}\mathbf{z}$? Note

that many AC electrical appliances produce 60 Hz, music is commonly

$\mathbf{400}\mathbf{H}\mathbf{z}$, a reference frequency is$\mathbf{1000}\mathbf{H}\mathbf{z}$, your maximum sensitivity

is near$\mathbf{4000}\mathbf{H}\mathbf{z}$, and many older TVs produce a$\mathbf{15},\mathbf{750}\mathbf{H}\mathbf{z}$whine.

Short answer

For $60Hz$,$400Hz$,$1000Hz$,$4000Hz$,$15000Hz$ frequencies have a threshold of hearing $44dB$,$10dB$,$0dB$,$-7dB$,$20dB$ respectively.

Step-by-step solution

Threshold of hearing

The threshold of hearing is the minimum sound level below which a person can't hear any sound. and loudness for barely audible is 0phons

Figure for sound level, intensity, and loudness at given frequencies

First, make a vertical line for all given frequencies and draw a horizontal line corresponding to these vertical lines then we will get our sound intensity levels in dB as shown in the figure.

This figure has a frequency(Hz) on the x-axis, intensity sound level (dB) on the y-axis, and a curved line showing the behavior of loudness(phons) corresponding to frequency and sound level.

Analysis of this figure

• Here we are interested in points that are crossings of vertical lines and0-phon curve
• Now make horizontal lines corresponding to these points that are crossings of vertical lines and0-phon curve, this horizontal line will meet on the y-axis at some value of sound level.

We got the following from the figure.

• For$60Hz$frequency, horizontal line cut y-axis around $44dB$ (threshold hearing)

• For$400Hz$frequency, horizontal line cut y-axis around $10dB$ (threshold hearing)
• For$1000Hz$frequency, horizontal line cut y-axis around $0dB$ (threshold hearing)
• For$4000Hz$frequency, horizontal line cut y-axis around $-7dB$ (threshold hearing)
• For$15000Hz$frequency, horizontal line cut y-axis around $20dB$ (threshold hearing)