Sound: speed, pitch and loudness

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   A speaker measures 100 dB at 1 m. Sound spreads evenly, so intensity falls with the square of distance. What level is heard at 10 m, to the nearest dB, Ari?

   80 dB
2. 2.

   A speaker measures 94 dB at 2 m. Sound spreads evenly, so intensity falls with the square of distance. What level is heard at 20 m, to the nearest dB, Bo?

   74 dB
3. 3.

   A speaker measures 88 dB at 1 m. Sound spreads evenly, so intensity falls with the square of distance. What level is heard at 4 m, to the nearest dB, Esme?

   76 dB
4. 4.

   A sound's pressure amplitude doubles. Intensity goes with amplitude squared. By about how much does the level rise, Jun?

   • About 12 dB
   • About 3 dB
   • About 6 dB
   • About 10 dB
5. 5.

   A 70 dB sound and a 60 dB sound are played together. About what level results, Kira?

   • About 80 dB, since 70 + 10 is 80
   • About 130 dB, since the two levels add together
   • About 70 dB, since the louder sound dominates
   • About 65 dB, the average of the two

6. Read this first

   Sound levels (NIDCD)

   Sound	Level (dBA)
   normal conversation	60–70
   movie theater	74–104
   motorcycles and dirt bikes	80–110
   headphones at maximum volume	94–110
   fireworks show	140–160

7. 6.

   Using the table, how many times as intense is the top of the headphones range as the top of the conversation range, Luz?

   • 1,000 times
   • 40 times
   • 100,000 times
   • 10,000 times

8. Speed of sound in air (example data, rounded)

   Air temperature (°C)	Speed (m/s)
   0	331
   40	355

9. 7.

   A 500 Hz note travels through 40 °C air. What is its wavelength, Milo?

   • 1.41 m
   • 0.66 m
   • 0.69 m
   • 0.71 m
10. 8.

    Noah hears a clap's echo 0.50 s later on a 0 °C day and 0.50 s later on a 40 °C day. Which cliff is farther, and by how much?

    • The 40 °C cliff, by about 12 m
    • The 40 °C cliff, by about 6 m
    • They are the same distance, since the delays are equal
    • The 0 °C cliff, by about 6 m
11. 9.

    Pia stands 200 m from a hammer blow on a long steel pipe. Sound travels at 5940 m/s in the steel and 343.3 m/s in air. What is heard?

    • The air sound first, about 0.55 s ahead of the steel sound that follows it
    • Both sounds together, since the start is the same
    • The steel sound first, about 0.55 s ahead of the air sound
    • The steel sound first, about 0.58 s ahead
12. 10.

    A guitar string vibrates at 220 Hz. Ren presses it at its midpoint, so half its length vibrates. What is the new frequency?

    • 440 Hz
    • 220 Hz, since the tension is unchanged
    • 880 Hz
    • 110 Hz