DECIBEL EXERCISE SHEET

SET 1: The decibel for a ratio of powers.

1) Express 10,000,000 watts in dB re: 1 watt.

2) Express 0.0001 watts in dB re: 1 watt.

3) Express 10,000 watts in dB re: 100 watts.

4) Express 10,000 watts in dB re: 0.01 watts.

SET 2: The decibel for ratios of other quantities.

1) Express 10 watts/cm² in dB re: 100,000 watts/cm².

2) Express 10,000 ergs in dB re: 10 ergs

3) Express 10,000 dynes/cm² in dB re: 10 dynes/cm²

4) Express 1 ubar in dB re: 0.0001 ubar

SET 3: Changes in dB, the effect of doubling and halving.

1) If a sound is increased (decreased) in power by a factor of 10, its dB value increases (decreases) by ____ ?

2) If a sound is increased (decreased) in pressure by a factor of 10, its dB value increases (decreases) by ____ ?

3) If a sound is increased (decreased) in power by a factor of 2, its dB value increases (decreases) by ____ ?

4) If a sound is increased (decreased) in pressure by a factor of 2, its dB value increases (decreases) by ____ ?

5) If the original intensity of a sound is 20 dB re: 1 watt, what is its intensity in dB re: 1 watt if its power is increased by a factor of 10? _____ , by a factor of 100? _____, by a factor of 2? ____, by a factor of 4? _____.

6) If the original intensity of a sound is 40 dB re: 1 ubar, what is its intensity in dB re: 1 ubar if its pressure is doubled? ____, halved? ____, quadrupled? _____.

SET 4: Changes in dB with unit conversions.

1) A sound 11 dB re: 1 watt is how many dB re: 2 watts?____ re: 0.1 watts? ____.

2) A sound 74 dB re: 1 ubar is how many dB re: 2 ubar?____ re: 0.0002 ubar? ____.

3) A sound -74 dB re: 1 ubar is how many dB SPL?____.

4) A sound 10 dB re: 1 ubar is how many dB SPL?____.

SET 5: In-Head Estimation Problems.

1) 10log(21/1.2) = _____.

2) 20log(127839.1/3443.2) = _____.

3) 64 dB re: 0.00024 dynes/cm^2 in SPL _____.

4) dB change is sound power if power is increased by a factor of 41.1 _____.

SET 6: Word Problems.

1) Sound-pressure level at 3 feet from a typical tornado siren is about 115 dB SPL. What is the Sound-pressure level at 300 feet from the siren?

2) A 1000-Hz band of noise has 100 times the total power of a 10-Hz band of noise. If the level of the 1000-Hz band is 50 dB SPL, what is the level of the 10-Hz band?

3) At 0 dB SPL speech is just barely audible. Soft speech is about 1000 times more intense than barely audible speech. What is the SPL of soft speech?

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