U H d2l.laurentian.ca B Exp'l_lnstructiuns-PHYS1007ERevised E Experiment 1 Sound Waves 1. Purpose To study physical characteristics of sound waves. 2. Introduction We focus our attention now on sound waves, which travel through any material, but are most commonly experienced as the mechanical waves traveling through air that result in the human perception of hearing. As sound waves travel through air, elements of air are disturbed from their equilibrium positions. Accompanying these movements are changes in density and pressure of the air along the direction of wave motion. Download the Phyphox app onto your cell phone. Start Phyphox and select the Audio Amplitude tab which records short intervals from the microphone and calculates the sound pressure level (SPL). The sound pressure level (SPL) is the pressure level of a sound, measured in decibels (dB). It is equal to SPL(db) = 201og10 (Pi) = 1010g10( P 2 I a) 1010g10 3 Eq. 1 U H d2l.laurentian.ca B Exp'l_lnstructiuns-PHYS1007ERevised E where P is the absolute sound pressure, P0 is the reference of sound pressure of 2 X 10'5 Pa, I is the absolute intensity, and I0 is the reference sound intensity equal to 10'12 W/mz. In this lab your cell phone/phyphox app will provide recording SPL values as a mction of time. You will be exporting this data from your phone to your computer. Then with Matlab you will be able to calculate the mean values and the standard deviation of the SPL values. Using this mean value, you can then rearrange Eq.1 to obtain the pressure amplitude P given by 1 sp P = P0 X 105 Eq. 2 In terms of P the expression for the intensity is given by Eq. 3 where p is the density of air and v is the speed of sound in air. Table 1 gives these values for air as a function of temperature. PHYS 1007E-Lab Winter 2022, Experiment 1 Page 1 of 5 Table 1: Effect of temperature on properties of air. d21.laurentian.ca + my Front Page - myLaurentian B Exp1_Instructions-PHYS1007E-Revised -... Homework Help - Q&A from Online Tutor. PHYS1007ELL - Introductory Physics II -... G sound waves acronym - Google Search Table 1: Effect of temperature on properties of air. Speed of Density Temperature, sound, c of air, p T ( C) (m/s) (kg/m3) 35 351.88 1.1455 30 349.02 1.1644 25 346.13 1.1839 20 343.21 1.2041 15 340.27 1.2250 10 337.31 1.2466 5 334.32 1.2690 0 331.30 1.2922 -5 328.25 1.3163 -10 325. 18 1.3413 -15 322.07 1.3673 -20 318.94 1.3943 -25 315.77 1.4224 Ref: WikipediaR Assuming an isotropic source, the intensity at a distance r from the sound source is given by Power I = Power Ea. 4U H d2l.laurentian.ca B Exp'l_lnstructiuns-PHYS1007ERevised E Assuming an isotropic source, the intensity at a distance r from the sound source is given by I = Power = Power Eq- 4 A 4m2 where the Power is the average power emitted by the source expressed in Watts. The intensity decreases as the square of the distance from the source, an inverse square law. Page 2 of 5 PHYS 1007E-Lab Winter 2022, Experiment 1 Question 1 A reworks rocket explodes at a height of 100 m above the ground. An observer on the ground directly under the explosion experiences an average sound intensity of 7.00 x 10'2 W/m2 for 0.2 s. (a) What is the total amount of energy transferred away from the explosion by sound? (b) What is the sound pressure level (in decibels) heard by the observer? Here since we know information about the ___ _ . _ m ___ U H d2l.laurentian.ca B Exp'l_lnstructiuns-PHYS1007ERevised E Question 1 A reworks rocket explodes at a height of 100 m above the ground. An observer > on the ground directly under the explosion experiences an average sound intensity of 7.00 x 10'2 W/m2 for 0.2 s. (a) What is the total amount of energy transferred away from the explosion by sound? (b) What is the sound pressure level (in decibels) heard by the observer? Here since we know information about the intensity, use the expression SPL = 10 log am) with L,=10'12 W/mz. Note: In the actual lab, please use SPL = 20 log (P/Po) with P[,=2>