Question

similar to Ch. 17, #68 as in the picture below, but change to: 2.5 m 4m 686 Hz > 440 Hz Temperature 30.15 Kelvin (gives the speed of sound) "hear a minimum" === > "hear a MAXIMUM" 68. | You are standing 2.5 m directly in front of one of the two loudspeakers shown in FIGURE P17.68. They are 3.0 m apart and both are playing a 686 Hz tone in phase. As you begin to walk directly away from the speaker, at what dis tances from the speaker do you hear a minimum sound intensity? The room temperature is 20°C. Walk 2.5 m 3.0 m FIGURE P17.68

Answer 1

Given, r = adiabatic constant 440 frequency (f) = 440Hz Tenu T = 30.15k Vsound = FORT R = as constant VM M = molecular mass of gas. for dry air 8=1.4, R = 8.314 J/molk M = 28.95 g/mol carg) V = 1.488.314830.15 = 110.100 m/s 28.95 wavelength & = x + = 110.100x1/2 - 0.250m To heas maximum sound intensity at a point (Q) path difference - Integer multiple of a BO - AQ = nd, where = integer 13+AR? - AQ = "X0.250 let & is at P = AO = AP = 4m. √ 3² +42 - 4 = 0.250 n-5-4 = 4 so P is the point where sound Entensity will be maximum Next maximum will again meet at n=3 = √3²+ AQ² _ AQ = 5x0.250 - AQ = 5.625 m