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Exploring Acoustics in the Hopkins Center. Scott Niehaus. Background. Sound that is emitted propagates in all directions as a wave and strikes all surfaces in its path Sound can be absorbed, reflected, or transmitted by a surface
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Exploring Acoustics in the Hopkins Center Scott Niehaus
Background • Sound that is emitted propagates in all directions as a wave and strikes all surfaces in its path • Sound can be absorbed, reflected, or transmitted by a surface • Soft surfaces like carpets tend to absorb sound while hard surfaces like walls reflect sound • Absorption coefficients range from 0-1, with 0 meaning totally reflecting and 1 meaning totally absorbing • Engineers target reverberation times of .8-1.0 seconds for band or orchestral rehearsal spaces and 1.0-1.3 seconds for choral rehearsal spaces
Upper Buck • Room Characteristics: shaped like an oval, lots of hard walls and glass, 93.8 m3 • Average reverberation time: 0.88 seconds • Sabine’s formula: T60 = .161V/S • Absorption coefficient of room: .09 • ART with carpets and comforter: 0.72 seconds
Upper Buck (cont.) • Adding carpets and my comforter did not greatly affect the spectrogram of a piano chord, it only changed the reverb time
Lower Buck • Room Characteristics: more rectangular, all walls, larger than UB • Average reverberation time: 0.44 seconds • ART with carpets and comforter: 0.42 seconds • Absorption coefficient of room: unable to measure
Individual Practice Room • Room Characteristics: 15.6 m3, small box, all walls, but not as smooth as upper buck • Average reverberation time: 0.25 seconds • Absorption coefficient of room: .265 • RT with comforter: 0.21 seconds • Absorption coefficient of room with comforter: .314
Absorption Coefficients • From the data I gathered I was able to figure out the absorption coefficients of my comforter and the 3 rugs I used. • Absorption coefficient of my 3.5 m2 comforter: 0.796 • Absorption coefficient of 3 rugs totaling 2.7 m2 : 0.30
Piano Analysis Short C Major chord bursts of the same volume produce significantly different spectrograms in the 3 rooms
Conclusions • Room shape, size, and types of surfaces present all affect reverberation times and sound quality • When played on a piano, the shorter RTs corresponded harsher timbres • Individual rehearsal rooms do not need a long RT as there is nothing to blend with when playing alone • Higher sound quality of Upper Buck vs. Lower Buck corresponds with sentiments of my a cappella group