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 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 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 seconds for band or orchestral rehearsal spaces and seconds for choral rehearsal spaces Engineers target reverberation times of seconds for band or orchestral rehearsal spaces and seconds for choral rehearsal spaces

Upper Buck Room Characteristics: shaped like an oval, lots of hard walls and glass, 93.8 m 3 Room Characteristics: shaped like an oval, lots of hard walls and glass, 93.8 m 3 Average reverberation time: 0.88 seconds Average reverberation time: 0.88 seconds Sabine’s formula: T 60 =.161V/S Sabine’s formula: T 60 =.161V/S Absorption coefficient of room:.09 Absorption coefficient of room:.09 ART with carpets and comforter: 0.72 seconds 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 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 Room Characteristics: more rectangular, all walls, larger than UB Average reverberation time: 0.44 seconds Average reverberation time: 0.44 seconds ART with carpets and comforter: 0.42 seconds ART with carpets and comforter: 0.42 seconds Absorption coefficient of room: unable to measure Absorption coefficient of room: unable to measure

Individual Practice Room Room Characteristics: 15.6 m 3, small box, all walls, but not as smooth as upper buck Room Characteristics: 15.6 m 3, small box, all walls, but not as smooth as upper buck Average reverberation time: 0.25 seconds Average reverberation time: 0.25 seconds Absorption coefficient of room:.265 Absorption coefficient of room:.265 RT with comforter: 0.21 seconds RT with comforter: 0.21 seconds Absorption coefficient of room with comforter:.314 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. 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 m 2 comforter: Absorption coefficient of my 3.5 m 2 comforter: Absorption coefficient of 3 rugs totaling 2.7 m 2 : 0.30 Absorption coefficient of 3 rugs totaling 2.7 m 2 : 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 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 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 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 Higher sound quality of Upper Buck vs. Lower Buck corresponds with sentiments of my a cappella group

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