ET III Adam Joseph Lewis Building

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ET IIIAdam Joseph Lewis Building
ACOUSTICAL ANALYSIS OF 201 Feb. 19, 2004
Brian Avery Joshua Haney Steven Scott
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HYPOTHESIS

• The reverberation time at mid frequencies in
  room 201 is less than or equal to .8 seconds
  the ideal reverberation time for speech clarity
  in a classroom.

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PROCESS 1

• Create test tones at 250, 500, 1000, 2000, and
  4000 Hz
• Record them.
• Analyze them in Spectrogram 8.
• In Excel, graph sound level (dB) over time (sec).
• Reverberation time (Tr) at each frequency is the
  time the sound level takes to decrease 60 dB.

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PROCESS 2

• Calculate room volume.
• Calculate surface area of all materials.
• Look up sound absorption coefficients of each
  material.
• Calculate reverberation time at each frequency.
• Tr .05 V/sabins
• sabins surface area X coefficient

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ROOM 201
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ROOM 201
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CALCULATIONS

• WEST WALL
• MATERIAL AREA (sq ft) X 250 500 1000 2000 40
  00
• GYP BOARD 178.5 .10 .05 .04 .07 .09
• GLASS 48.0 .06 .04 .03 .02 .02
• WOOD 51.25 .11 .10 .07 .06 .07
• SHADES 45.0 .08 .06 .05 .04 .04
• TOTAL SABINS 30.0 18.6 14.4 18.3 22.9

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CALCULATIONS

• EAST WALL
• MATERIAL AREA (sq ft) X 250 500 1000 2000 4
  000
• GLASS 42.0 .06 .04 .03 .02 .02
• WOOD 51.25 .11 .10 .07 .06 .07
• CMU 164.5 .05 .06 .07 .09 .08
• STEEL 20.0 .06 .04 .03 .02 .02
• SHADES 45.0 .08 .06 .05 .04 .04
• TOTAL SABINS 21.1 20.2 24.7 20.9 19.7

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CALCULATIONS

• NORTH WALL
• MATERIAL AREA (sq ft) X 250 500 1000 2000 4
  000
• GYP BOARD 363.5 .10 .05 .04 .07 .09
• GLASS 42.0 .06 .04 .03 .02 .02
• WOOD 51.5 .11 .10 .07 .06 .07
• SHADES 280.0 .08 .06 .05 .04 .04
• TOTAL SABINS 66.9 41.9 33.4 40.5 48.3

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CALCULATIONS

• SOUTH WALL
• MATERIAL AREA (sq ft) X 250 500 1000 2000 4
  000
• GLASS 236.5 .06 .04 .03 .02 .02
• CMU 270.0 .05 .06 .07 .09 .08
• STEEL 47.0 .06 .04 .03 .02 .02
• TOTAL SABINS 30.5 27.6 27.4 29.9 27.2

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FLOOR

• MATERIAL AREA (sq ft) X 250 500 1000 2000 4
  000
• CARPET 846.0 .06 .14 .37 .60 .65
• TOTAL SABINS 50.76 118.44 313.02 507.6 549.9

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CEILING

• MATERIAL AREA (sq ft) X 250 500 1000 2000 4
  000
• WOOD 51.5 .11 .10 .07 .06 .07
• TOTAL SABINS 90.2 82.0 57.4 49.2 57.4

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CALCULATIONS

• Tr(250)
• TOTAL SABINS 289.5
• V 13,345
• .05 V/T 2.3 sec
• Tr(500)
• TOTAL SABINS 308.7
• V 13,345
• .05 V/T 2.2 sec
• Tr(1000)
• TOTAL SABINS 470.3
• V 13,345
• .05 V/T 1.4 sec
• Tr(2000)
• TOTAL SABINS 667.3
• V 13,345
• .05 V/T 1.0 sec
• Tr(4000)
• TOTAL SABINS 725.4
• V 13,345

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CONCLUSIONS

• The calculated reverberation times were all over
  .8 seconds. The reverberation time in room 201
  is not ideal for a classroom setting.
• Reverberation time could be decreased by adding
  more Sabins for total room absorption. Possible
  sources of absorption could be upholstered chairs
  or sound absorbing material placed on the concave
  ceiling.