Answer:
5.65 times
Explanation:
60 db sound is equal to 60 phons sound when frequency is kept at 1000Hz.
But when the frequency of sound is changed to 100 Hz , according to equal loudness curves , the loudness level on phon scale will be 35 phons.
A decrease of 10 phon on phon- scale makes sound 2 times less loud
Therefore a decrease of 25 phons will make loudness less intense by a factor equal to 2²°⁵ or 5.65 less intense . Therefore intensity at 100 Hz
must be increased 5.65 times so that its intensity matches intensity of 60 dB sound at 1000 Hz frequency.
