Fact · Dictation
21.6decibels
Applying the inverse-square rule to a microphone at 12 inches instead of 1 inch gives a level difference of about 21.6 dB, under ideal free-field conditions.
Checked against its source on October 16, 2026
- What it measures
- A calculation for a close headset at about 1 inch versus a microphone about a foot away. Free-field conditions are an idealization, so this is an upper estimate of the physics in an ordinary room.
- How it is calculated
- 20 x log10(12 / 1) = 20 x 1.079 = 21.6 dB, using the distance ratio from the 6 dB rule (20 log(d1/d2)).
- What it does not show
- The calculation assumes the free-field rule holds, which is only approximately true near a source. It is a guide to scale, not a measurement of any particular laptop.
Calculated from
Cited on
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