Sound intensity and the decibel scale
Grade 11 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
A small speaker sends out 0.5 W of sound evenly in all directions. What is the intensity 4 m away, to 0.01 mW/m², Ari?
A small speaker sends out 2 W of sound evenly in all directions. What is the intensity 10 m away, to 0.01 mW/m², Bo?
A small speaker sends out 0.1 W of sound evenly in all directions. What is the intensity 2 m away, to 0.01 mW/m², Kira?
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.
Using the table, how many times as intense as a quiet home is normal conversation, Luz?
- 2 times
- 1000 times
- 30 times, one per decibel
Using the table, how many times as intense as a whisper at 1 m is busy traffic, Milo?
- 50 times, one per decibel
- 100,000 times
- 3.5 times
On the decibel ruler, a sound drops from 80 dB to 60 dB. What happens to its intensity, Pia?
- It falls to a hundredth
- It falls to a half
- It falls to three quarters
On the decibel ruler, what intensity sits at 30 dB, Ren?
Use the picture in question 6.
- 10⁻³⁰ W/m²
- 10⁻⁹ W/m²
- 30 × 10⁻¹² W/m²
What does sound intensity measure, by Tala's reading (OpenStax)?
- The pitch of the sound, in hertz
- The total power of the source, in watts
- The sound power passing through each square meter
What does 0 dB mean, by Zee's reading (OpenStax)?
- A sound too loud to measure
- Total silence, with zero intensity
- The faintest sound a person can hear, 10⁻¹² W/m²
A sound meter in a quiet room reads 0 dB. What does that show, Esme?
- There is no sound energy anywhere in the room
- The sound is right at the threshold of hearing
- The meter must be broken, since a room is not that quiet