Sound intensity and the decibel scale

Answer Key - Grade 11 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   A sound reads 65 dB. What is its intensity, to 0.01 μW/m², Esme? Use I₀ = 10⁻¹² W/m².

   3.16 μW/m²
2. 2.

   A sound reads 52 dB. What is its intensity, to 0.01 μW/m², Jun? Use I₀ = 10⁻¹² W/m².

   0.16 μW/m²
3. 3.

   A sound reads 78 dB. What is its intensity, to 0.01 μW/m², Kira? Use I₀ = 10⁻¹² W/m².

   63.1 μW/m²
4. 4.

   A student says an 80 dB sound has twice the intensity of a 40 dB sound. Which reply fits OpenStax, Luz?

   • Yes; twice the decibels means twice the intensity
   • No; it is 40 times as intense, one per decibel
   • No; it is 10,000 times as intense
5. 5.

   A student says moving twice as far from a speaker halves the intensity. Which reply fits OpenStax, Milo?

   • Yes; intensity falls in step with distance
   • No; it falls to a quarter, as 1 ÷ r²
   • Yes; twice as far, half the sound energy per square meter
6. 6.

   A student says a 0 dB reading means there is no sound energy at all. Which reply fits OpenStax, Noah?

   • No; 0 dB is one unit of intensity, and 10 dB is two units
   • No; 0 dB is 10⁻¹² W/m², the faintest sound heard
   • Yes; 0 dB means zero intensity
7. 7.

   A speaker gives 70 dB at 2 m. About what level is it at 4 m, Pia?

   • About 64 dB
   • About 35 dB
   • About 67 dB
8. 8.

   A speaker gives 60 dB at 10 m. About what level is it at 1 m, Ren?

   • About 80 dB
   • About 600 dB
   • About 70 dB
9. 9.

   A speaker gives 74 dB at 1 m. About what level is it at 2 m, Tala?

   • About 68 dB
   • About 71 dB
   • About 37 dB
10. 10.

    A spot gets 70 dB from one machine. A second, identical machine also gives 70 dB at that spot. About what is the total, Bo?

    • About 73 dB
    • About 140 dB
    • About 80 dB