Sound with intensity larger than 120 dB appears painful to a person. A speaker delivers 280 W of audio output. How close can the person get to the speaker without feeling pain?
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- Question 2 a) Give the equation relating the acoustic impedance of a medium Z to its density p and the speed of sound/ultrasound in that medium c. b) The following table gives the density of some different media and the speed of ultrasound through them. Medium Density / kg m3 Ultrasound velocity/m s1 Air 1.3 330 Fat 925 1450 Muscle 1075 1590 Bone 1650 4080 (Z2-Z,)2 (Z2+Z1)² %3D Use this information and the above equation to calculate the ratio a of the reflected ultrasound intensity I, to the incident intensity I, at the interface between i) air and fat ii) fat and muscle iii) fat and boneThe sound level 23.8 m from a loudspeaker is 66.7 dB. What is the rate at which sound energy is produced by the loudspeaker, assuming it to be an isotropic source?The acoustic impedance of water is Zwater = 1440000 kg/(m2 s), and that of bone is Zbone = 7800000 kg/(m2 s). What proportion of the energy of a sound wave propagating in water will be reflected at the water-bone boundary?
- Two loudspeakers, A and B, are driven by the same amplifier and emit sinusoidal waves in phase. The frequency of the waves emitted by each speaker is 708 Hz. You are standing between the speakers, along the line connecting them and are at a point of constructive interference. How far must you walk toward speaker B to move to reach the first point of destructive interference? Take the speed of sound to be 344 m/s. Express your answer in meters.A loudspeaker on a tall pole broadcasts sound waves equally in all directions. What is the speaker’s power (in watts) output if the sound intensity level is 90 dB at a distance of 25 m? Hint: Assume the pole is tall enough that we don’t have to worry about the ground absorbing or reflecting sound. The intensity is Intensity (I) = Power (P)/Area(A). At a far point (r) from the source A =4 pi r2The volume control on a surround-sound amplifier is adjusted so the sound intensity level at the listening position increase from 23 to 66 dB. What is the ratio of the final sound intensity to the original sound intensity? Number i Units
- A sound wave enters the thin tube at P and exits at Q. Assume r = 0.50m and the wavelength is 1.12m. What is the smallest length d that results in constructive interference at Q?Ultrasound with frequency 11.3 MHz is passing through fat. The ultrasound travels at the speed of 1450 m/s in the fat. The ultrasound wave reaches the liver and some portion transmits through the liver. The acoustic impedance of the liver is Z= 1650000 kg/m^2s What is the wavelength of the ultrasound in the fat? What is the acoustic impedence of the fat?(p+920 kg/m^3 for the fat What is the proportion of the ultrasound energy reflected at the fat liver boundary? What is the speed of ultrasound int the liver? p= 1015 kg/m^3 for the liver What is the wavelength of the ultrasound in the liverA sound wave travels through air at 20 °C. The decibel level at a distance of 19.4 m from the source is measured to be 85.2 dB. What is the dB level at a position that is 7.17 m closer? Assume the density of air is 1.20 kg/m3 and that the source produces spherical wave fronts.
- Yellow light travels at a speed of 1.97 108 m/s through a certain glass block. The wavelength of light transmitted through this kind of glass is 3.835 10-7 m. What frequency does yellow light have?Hz.30 seconds of exposure to 115 dB sound can damage your hearing, but a much quieter 94 dB may begin to cause damage after 1 hour of continuous exposure. You are going to an outdoor concert, and you’ll be standing near a speaker that emits 50 W of acoustic power as a spherical wave. What minimum distance should you be from the speaker to keep the sound intensity level below 94 dB?A stereo speaker is placed between two observers who are 36 m apart, along the line connecting them. If one observer records an intensity level of 60 dB, and the other records an intensity level of 80 dB, how far is the speaker from each observer?