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{
"metadata": {
"name": "",
"signature": "sha256:3bec68600cdf231538bf44a09963d76f89f72c71634091075e5c4136c75bb4a6"
},
"nbformat": 3,
"nbformat_minor": 0,
"worksheets": [
{
"cells": [
{
"cell_type": "heading",
"level": 1,
"metadata": {},
"source": [
"18: Acoustics of Buildings"
]
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 18.1, Page number 361"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
" \n",
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"r = 200; #Distance of the point of reduction from the source(m)\n",
"I_0 = 10**-12; #Final intensity of sound(W/m**2)\n",
"I_f = 60; #Intensity gain of sound at the point of reduction(dB)\n",
"\n",
"#Calculation\n",
"#As A_I = 10*log10(I/I_0), solving for I\n",
"I = I_0*10**(I_f/10); #Initial Intensity of sound(W/m**2)\n",
"P = 4*math.pi*r**2*I; #Output power of the sound source(W)\n",
"P = math.ceil(P*100)/100; #rounding off the value of P to 2 decimals\n",
"\n",
"#Result\n",
"print \"The output power of the sound source is\",P, \"W\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The output power of the sound source is 0.51 W\n"
]
}
],
"prompt_number": 1
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 18.2, Page number 361"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
" \n",
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"import numpy as np\n",
"\n",
"#Variable declaration\n",
"I1 = 1; #For simplicity assume first intensity level to be unity(W/m**2)\n",
"\n",
"#Calculation\n",
"I2 = 2*I1; #Intensity level after doubling(W/m**2)\n",
"dA_I = 10*np.log10(I2/I1); #Difference in gain level(dB)\n",
"\n",
"#Result\n",
"print \"The sound intensity level is increased by\",int(dA_I), \"dB\""
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The sound intensity level is increased by 3 dB\n"
]
}
],
"prompt_number": 3
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 18.3, Page number 361"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
" \n",
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"V = 8000; #Volume of the hall(m**3)\n",
"T = 1.5; #Reverbration time of the hall(s)\n",
"\n",
"#Calculation\n",
"alpha_s = 0.167*V/T; #Sabine Formula giving total absorption of sound in the hall(OWU)\n",
"alpha_s = math.ceil(alpha_s*10)/10; #rounding off the value of alpha_s to 1 decimal\n",
"\n",
"#Result\n",
"print \"The total absorption of sound in the hall is\",alpha_s, \"OWU\"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The total absorption of sound in the hall is 890.7 OWU\n"
]
}
],
"prompt_number": 4
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 18.4, Page number 362"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
"\n",
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"V = 25*20*8; #Volume of the hall(m**3)\n",
"T = 4; #Reverbration time of the hall(s)\n",
"\n",
"#Calculation\n",
"S = 2*(25*20+25*8+20*8); #Total surface area of the hall(m**2)\n",
"alpha = 0.167*V/(T*S); #Sabine Formule giving total absorption in the hall(OWU)\n",
"alpha = math.ceil(alpha*10**4)/10**4; #rounding off the value of alpha to 4 decimals\n",
"\n",
"#Result\n",
"print \"The average absorption coefficient of the surfaces is\",alpha, \"OWU/m**2\"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The average absorption coefficient of the surfaces is 0.0971 OWU/m**2\n"
]
}
],
"prompt_number": 5
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 18.5, Page number 362"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
" \n",
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"V = 475; #Volume of the hall(m**3)\n",
"A_f = 100; #Area of the floor(m**2)\n",
"A_c = 100; #Area of the ceiling(m**2)\n",
"A_w = 200; #Area of the wall(m**2)\n",
"alpha_w = 0.025; #Absorption coefficients of the wall(OWU/m**2)\n",
"alpha_c = 0.02; #Absorption coefficients of the ceiling(OWU/m**2)\n",
"alpha_f = 0.55; #Absorption coefficients of the floor(OWU/m**2)\n",
"\n",
"#Calculation\n",
"alpha_s = (A_w*alpha_w)+(A_c*alpha_c)+(A_f*alpha_f); \n",
"T = 0.167*V/alpha_s; #Sabine Formula for reverbration time(s)\n",
"T = math.ceil(T*100)/100; #rounding off the value of T to 2 decimals\n",
"\n",
"#Result\n",
"print \"The reverbration time for the hall is\",T, \"s\"\n"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The reverbration time for the hall is 1.28 s\n"
]
}
],
"prompt_number": 6
},
{
"cell_type": "heading",
"level": 2,
"metadata": {},
"source": [
"Example number 18.6, Page number 362"
]
},
{
"cell_type": "code",
"collapsed": false,
"input": [
" \n",
"#importing modules\n",
"import math\n",
"from __future__ import division\n",
"\n",
"#Variable declaration\n",
"I0 = 1; #For simplicity assume initial sound intensity to be unity(W/m**2)\n",
"A_I1 = 80; #First intensity gain of sound(dB)\n",
"A_I2 = 70; #Second intensity gain of sound(dB)\n",
"\n",
"#Calculation\n",
"#As A_I = 10*log10(I/I_0), solving for I1 and I2\n",
"I1 = 10**(A_I1/10)*I0; #First intensity of sound(W/m**2)\n",
"I2 = 10**(A_I2/10)*I0; #Second intensity of sound(W/m**2)\n",
"I = I1 + I2; #Resultant intensity level of sound(W/m**2)\n",
"A_I = 10*np.log10(I/I0); #Intensity gain of resultant sound(dB)\n",
"A_I = math.ceil(A_I*10**3)/10**3; #rounding off the value of A_I to 3 decimals\n",
"\n",
"#Result\n",
"print \"The intensity gain of resultant sound is\",A_I, \"dB\"\n",
"\n",
"#answer given in the book is wrong"
],
"language": "python",
"metadata": {},
"outputs": [
{
"output_type": "stream",
"stream": "stdout",
"text": [
"The intensity gain of resultant sound is 80.414 dB\n"
]
}
],
"prompt_number": 7
},
{
"cell_type": "code",
"collapsed": false,
"input": [],
"language": "python",
"metadata": {},
"outputs": []
}
],
"metadata": {}
}
]
}
|
