So a noise that is 30 db louder is 1000 times as loud. Here's a list of common activities with an estimated sound intensity level. Our gain of 1.3 Bels is equivalent to 13 decibels. To convert to decibels, simply multiply the number of Bels by 10. The decibel scale defines the threshold of hearing at 0 decibels and the threshold of pain at 130 decibels. The result is the decibel (one-tenth Bel). Since the range of hearing is so large, scientists invented a logarithmic scale which is based on multiples of 10. The loudest sound we can hear is about 1,000,000,000 times louder than the softest sound we can hear. Human hearing is extremely versatile, being able to hear very soft sounds from 10-12 W/m2 to very loud sounds at 1 W/m2 where the sound starts to become painful. You can still see pipes in old ships that the captain used to give commands to others in distant parts of the vessel. Note that if you make a sound in an enclosed area, especially one with hard walls that do not absorb energy, e.g., like a pipe, the intensity will not drop off with distance. If a sound is made in an open area, the intensity drops off quickly as you get farther from the source because the sound energy is spread in every direction. A microphone will measure the intensity of a sound and display the difference in the amplitude of the pressure plot. The more energetic the speaker, between speaking and yelling, the more energy is present in the resulting wave. Sound amplitude is a measure of the energy in a sound wave. It is measured in watts per square meter. In pressure terms, intensity is a measure of the amount of compression and rarefaction of the sound pressure wave. With this note, I am calling attention to a case of the application of a. Yet students often have difficulty mastering the concept of logarithmic scales. One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio. If the wavelength of these waves is 34 m, what is their speed? Solution:Ĭhapter 14 Waves and Sounds Q.3CQ At a ball game.The Physics of Sound in Non-Scientific Language >Ī sound not only has the property of frequency, it has volume, also known as amplitude or intensity. Logarithmic intensity scales are widely encountered in astronomy (star magnitudes), acoustics (decibels), seismology (the Richter scale), and elsewhere. decibel (dB), unit for expressing the ratio between two physical quantities, usually amounts of acoustic or electric power, or for measuring the relative loudness of sounds. What are (a) the wavelength and (b) the amplitude of this wave? Solution:Ĭhapter 14 Waves and Sounds Q.2CQ Wriat type of wave ¡s exhibited by “amber waves of grain”? Solution: IWaves passing through a grain field are longitudinal waves I The motion of each grain stalk is in the same direction as the motion of the wave itselfĬhapter 14 Waves and Sounds Q.2P A surfer floating beyond the breakers notes 14 waves per minute passing her position. The vertical distance from crest to trough for this wave is 13 cm and the horizontal distance from crest to trough is 28 cm. How should you hit the nail with a hamm er to generate a longitudinal wave? How should you hit it to generate a transverse wave? Solution: For generating a longitudinal wave, jwe hit the nail on the head in the direction parallel to its length[ In order to generate transverse waves, the nail is hit ¡n a direction perpendicular to its IengthĬhapter 14 Waves and Sounds Q.1P A wave travels along a stretched horizontal rope. Mastering Physics Solutions Chapter 14 Waves and SoundsĬhapter 14 Waves and Sounds Q.1CQ A long nail has been driven halfway into the side of a barn.
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