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

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

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

6. Read this first

   Speed of sound in air (example data, rounded)

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

7. 6.

   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 0 °C cliff, by about 6 m
   • They are the same distance, since the delays are equal
   • The 40 °C cliff, by about 6 m
8. 7.

   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?

   • Both sounds together, since the start is the same
   • The steel sound first, about 0.55 s ahead of the air sound
   • The air sound first, about 0.55 s ahead of the steel sound that follows it
   • The steel sound first, about 0.58 s ahead
9. 8.

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

   • 220 Hz, since the tension is unchanged
   • 880 Hz
   • 440 Hz
   • 110 Hz
10. 9.

    A string vibrates at 220 Hz. Tala makes its tension 9 times as large. Wave speed goes with the square root of tension. What is the new frequency?

    • 1,980 Hz
    • 73 Hz
    • 440 Hz
    • 660 Hz
11. 10.

    Zee hears 3 beats each second between a 440 Hz fork and a guitar string. What could the string's frequency be?

    • 437 Hz, since the string must be lower than the fork
    • Either 437 Hz or 443 Hz
    • 443 Hz, since the string must be higher than the fork
    • 1,320 Hz, three times the fork's frequency