Sound intensity and the decibel scale

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   A sound has an intensity of 0.000002 W/m². What is its level, to 0.1 dB, Bo? Use I₀ = 10⁻¹² W/m².

   63 dB
2. 2.

   A sound has an intensity of 0.00005 W/m². What is its level, to 0.1 dB, Esme? Use I₀ = 10⁻¹² W/m².

   77 dB
3. 3.

   A sound has an intensity of 0.000009 W/m². What is its level, to 0.1 dB, Jun? Use I₀ = 10⁻¹² W/m².

   69.5 dB
4. 4.

   A listener moves from 2 m to 4 m from a small speaker. What happens to the intensity, Kira?

   • It falls to a quarter
   • It falls to an eighth
   • It falls to a half
5. 5.

   A listener moves from 3 m to 1 m from a small speaker. What happens to the intensity, Luz?

   • It becomes 6 times as intense
   • It becomes 3 times as intense
   • It becomes 9 times as intense
6. 6.

   The intensity 1 m from a speaker is 0.8 mW/m². What is it 4 m away, Milo?

   • 3.2 mW/m²
   • 0.05 mW/m²
   • 0.2 mW/m²
7. 7.

   One sound is 5 times as intense as another. About how many decibels higher is it, by Pia's reading (OpenStax)?

   • About 50 dB higher
   • About 7 dB higher
   • About 5 dB higher
8. 8.

   One sound is 1000 times as intense as another. How many decibels higher is it, Ren?

   • 30 dB higher
   • 1000 dB higher
   • 3 dB higher

9. Read this first

   Table, sound levels and intensities (OpenStax Table 17.2), with columns sound, level (dB) and intensity (W/m²)

   Rustle of leaves, 10, 10⁻¹¹; whisper at 1 m, 20, 10⁻¹⁰; quiet home, 30, 10⁻⁹; normal conversation, 60, 10⁻⁶; busy traffic, 70, 10⁻⁵; loud radio, 80, 10⁻⁴.

10. 9.

    Using the table, a sound is 100 times as intense as a quiet home. What is its level, Zee?

    • 130 dB
    • 3,000 dB
    • 50 dB
11. 10.

    Using the table, how does the intensity of busy traffic compare with normal conversation, Ari?

    • 10 dB, so 10 W/m² more
    • About 1.2 times as intense
    • 10 times as intense