18. Waves & Sound

A source emits sound spherically with a power of 2.2 × 10⁴ W. What is the minimum distance away from this sound that would be considered safe (a volume of 150 dB or less)?

What is the speed of sound in air (a) on a cold winter day in Minnesota when the temperature is -25°F, and (b) on a hot summer day in Death Valley when the temperature is 125°F?

For a person with normal hearing, the faintest sound that can be heard at a frequency of 400 Hz has a pressure amplitude of about 6.0 × 10^-5 Pa. Calculate the intensity.

Expensive amplifier A is rated at 280 W, while the more modest amplifier B is rated at 45 W. What output wattage amp would sound about twice as loud as the 45-W amp?

A loud factory machine produces sound having a displacement amplitude of 1.00 mm, but the frequency of this sound can be adjusted. In order to prevent ear damage to the workers, the maximum pressure amplitude of the sound waves is limited to 10.0 Pa. Under the conditions of this factory, the bulk modulus of air is 1.42 × 10⁵ Pa. What is the highest-frequency sound to which this machine can be adjusted without exceeding the prescribed limit? Is this frequency audible to the workers?

You live on a busy street, but as a music lover, you want to reduce the traffic noise. If, instead, you reduce the intensity by half, what change (in dB) do you make in the sound intensity level?

A sound wave in air at 20°C has a frequency of 320 Hz and a displacement amplitude of 5.00 × 10^-3 mm. For this sound wave calculate the pressure amplitude (in Pa)

Example 16.1 (Section 16.1) showed that for sound waves in air with frequency 1000 Hz, a displacement amplitude of 1.2 × 10^-8 m produces a pressure amplitude of 3.0 × 10^-2 Pa. What is the wavelength of these waves?

A sound source is located somewhere along the x-axis. Experiments show that the same wave front simultaneously reaches listeners at x = -7.0 m and x = ＋3.0 m. What is the x-coordinate of the source?