Exam 14: Waves and Sound

A crying baby emits sound with an intensity of 8.0 × 10^-8 W/m².Calculate a reasonable estimate for the intensity level from a set of quintuplets (five babies),all crying simultaneously at the same place? The lowest detectable intensity is 1.0 × 10^-12 W/m².

Consider the standing wave on a guitar string and the sound wave generated by the string as a result of this vibration.What do these two waves have in common? (There may be more than one correct choice. )

Two in-phase loudspeakers are 3.0 m apart.They emit sound with a frequency of 490 Hz.A microphone is placed half-way between the speakers and then moved along the line joining the two speakers until the first point of constructive interference is found.At what distance from that midpoint is that first point? The speed of sound in air is 343 m/s.

If the intensity level by 15 identical engines in a garage is 100 dB,what is the intensity level generated by each one of these engines?

A certain glass window reduces the intensity level of the sound from 72 dB to 47 dB.By what factor is the acoustic power reduced by this glass window?

The average intensity of sunlight impinging on Earth is measured to be about 1.4 kW/m².What is the power of sunlight emitted by the sun? (Earth-Sun distance = 1.5 × 10⁸ km,Earth radius = 6.4 × 10³ km)

Sonar is used to determine the speed of an object.A 40.0-kHz signal is sent out,and a 42.0-kHz signal is returned.If the speed of sound is 345 m/s,how fast is the object moving?

A 25-g string is stretched with a tension of 43 N between two fixed points 12 m apart.What is the frequency of the second harmonic?

A music tuner uses a 554-Hz C# tuning fork to tune the frequency of a musical instrument.If the tuner hears a beat frequency of 2 Hz,what is the frequency of the instrument?

What is the wave speed in a brass wire with a radius of 0.500 mm stretched with a tension of 125 N? The density of brass is 8.60 × 10³ kg/m³.

By how many decibels does the intensity level of a sound decrease when you triple your distance from a source of sound?

The speed of sound in steel is 5000 m/s.What is the wavelength of a sound wave of frequency In steel?

A person stands between two speakers driven by the same source.Each speaker produces a tone with a frequency of 200 Hz on a day when the speed of sound is 330 m/s.The person is 1.65 m from one speaker and 4.95 m from the other.What type of interference does the person perceive?

The speed of sound through the ground is about 6.0 km/s while the speed of sound in air is 343 m/s.A very powerful explosion occurs some distance away and you feel the ground vibrate 60 seconds before you hear the sound of the explosion.How far away is the explosion?

A pipe that is 0.92 m long and open at both ends vibrates in the second overtone with a frequency of What is the speed of sound in the air in this pipe?

You double your distance from a sound source that is radiating equally in all directions.What happens to the intensity of the sound? It reduces to

Two tuning forks have frequencies of 440 and 522 Hz.What is the beat frequency if both are sounding simultaneously?

A violin with string length 32 cm and string density Resonates in its fundamental with the first overtone of a 2.0-m organ pipe with one end closed and one end open.What is the tension in the string if the speed of sound in air is 344 m/s?

Two taut strings of identical mass per unit length are stretched with the same tension with their ends fixed,but one string is 0.330 cm longer than the other.Waves on these strings propagate at 34.0 m/s.The fundamental frequency of the shorter string is 258 Hz.What is the beat frequency when each string is vibrating at its fundamental frequency?

A string of linear density 1.5 g/m is under a tension of 20 N.What should be its length if its fundamental resonance frequency is 220 Hz?