4. INTENSITY AND SOUND Use the following information for determining sound intensity. The number of decibels ß of a sound with an intensity of I watts per square meter is given by ß = 10 log (I/Io), where Io is an intensity of 10-12 watt per square meter, corresponding roughly to the faintest sound that can be heard by the human ear. Find the number of decibels ß of the sound. a) 1= 10° watt per m² (threshold of pain) b) I= 10² watt per m² (jet at 30 meters) c) I= 10¯8 watt per m² (quiet radio) d) 1= 10³ watt per m² (busy street corner)

4. INTENSITY AND SOUND Use the following information for determining sound intensity. The number of decibels ß of a sound with an intensity of I watts per square meter is given by ß = 10 log (I/Io), where Io is an intensity of 10-12 watt per square meter, corresponding roughly to the faintest sound that can be heard by the human ear. Find the number of decibels ß of the sound. a) 1= 10° watt per m² (threshold of pain) b) I= 10² watt per m² (jet at 30 meters) c) I= 10¯8 watt per m² (quiet radio) d) 1= 10³ watt per m² (busy street corner)

Physics for Scientists and Engineers, Technology Update (No access codes included)

9th Edition

ISBN:9781305116399

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter17: Sound Waves

Section: Chapter Questions

Problem 17.12OQ: With a sensitive sound-level meter, you measure the sound of a running spider as -10 dB. What does...

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(a) Ear trumpets were never very common, but they did aid people with hearing losses by gathering sound over a large area and concentrating it on the smaller area of the eardrum. What decibel increase does an ear trumpet produce it its sound gathering area is 900 cm2 and the area of the eardrum is 0.500 cm2, but the trumpet only has an eficiency of 5.00% in transmitting the sound to the eardrum? (b) Comment on the usefulness of the decibel increase found in part (a).
Calculate the speed of sound on a day when a 1500 Hz frequency has a wavelength of 0.221 m.
What frequency sound has a 0.10m wavelength when the speed of sound is 340 m/s?
A sound wave traveling in 20°C air has a pressure amplitude of 0.5 Pa. What is the intensity of the wave?
An ultrasonic tape measure uses frequencies above 20 MHz to determine dimensions of structures such as buildings. It does so by emitting a pulse of ultrasound into air and then measuring the time interval for an echo to return from a reflecting surface whose distance away is to be measured. The distance is displayed as a digital readout. For a tape measure that emits a pulse of ultrasound with a frequency of 22.0 MHz., (a) what is the distance to an object from which the echo pulse returns after 24.0 ms when the air temperature is 26C? (b) What should be the duration of the emitted pulse if it is to include ten cycles of the ultrasonic wave? (c) What is the spatial length of such a pulse?
With a sensitive sound-level meter, you measure the sound of a running spider as -10 dB. What does the negative sign imply? (a) The spider is moving away from you. (b) The frequency of the sound is too low to be audible to humans. (c) The intensity of the sound is too faint to be audible to humans. (d) You have made a mistake; negative signs do not fit with logarithms.
Based on the graph in Figure 17.36, what is the threshold of hearing in decibels for frequencies of 60, 400, 1000, 4000, and 15,000 Hz? Note that many AC electrical appliances produce 60 Hz, music is commonly 400 Hz, a reference frequency is 1000 Hz, your maximum sensitivity is near 4000 Hz, and many older TVs produce a 15,750 Hz whine. Figure 17.36 The relationship of loudness in phons to intensity level (in decibels) and intensity (in watts per meter squared) for persons with normal hearing. The curved lines are equal-loudness curves—all sounds on a given curve are perceived as equally loud. Phons and decibels are defined to be the same at 1000 Hz.
As a certain sound wave travels through the air, it produces pressure variations (above anti below atmospheric pressure) given by P = 1.27 sin (x - 34t) in SI units. Find (a) the amplitude of the pressure variations. (b) the frequency, (c) the wavelength in air. and (d| the speed of the sound wave.
Table 17.1 shows the speed of sound is typically an order of magnitude larger in solids than in gases. To what can this higher value be most directly attributed? (a) the difference in density between solids and gases (b) the difference in compressibility between solids and gases (c) the limited size of a solid object compared to a free gas (d) the impossibility of holding a gas under significant tension
Two eagles fly directly toward one another. The first at 15.0 m/s and the second at 20.0 m/s. Both screech, the first one emitting a frequency of 3200 Hz and the second one emitting a frequency of 3800 Hz. What frequencies do they receive if the speed of sound is 330 m/s?
Write an expression that describes the pressure variation as a function of position and time for a sinusoidal sound wave in air. Assume the speed of sound is 343 m/s, = 0.100 m, and Pmax = 0.200 Pa.
(a) Find the intensity in watts per meter squared of a 60.0Hz sound having a loudness of 60 phons. (b) Find the intensity in watts per meter squared of a 10,000—Hz sound having a loudness of 60 phons.