Exploring Acoustics Exploring Acoustics in the Hopkins Centerin the Hopkins Center

Scott NiehausScott Niehaus

BackgroundBackground

Sound that is emitted propagates in all Sound that is emitted propagates in all directions as a wave and strikes all surfaces in directions as a wave and strikes all surfaces in its pathits path

Sound can be absorbed, reflected, or Sound can be absorbed, reflected, or transmitted by a surfacetransmitted by a surface– Soft surfaces like carpets tend to absorb sound while Soft surfaces like carpets tend to absorb sound while

hard surfaces like walls reflect soundhard surfaces like walls reflect sound– Absorption coefficients range from 0-1, with 0 meaning Absorption coefficients range from 0-1, with 0 meaning

totally reflecting and 1 meaning totally absorbingtotally reflecting and 1 meaning totally absorbing Engineers target reverberation times of .8-1.0 Engineers target reverberation times of .8-1.0

seconds for band or orchestral rehearsal spaces seconds for band or orchestral rehearsal spaces and 1.0-1.3 seconds for choral rehearsal spacesand 1.0-1.3 seconds for choral rehearsal spaces

Upper BuckUpper Buck

Room Characteristics: shaped like an oval, lots of Room Characteristics: shaped like an oval, lots of hard walls and glass, 93.8 hard walls and glass, 93.8 mm33

Average reverberation time: 0.88 secondsAverage reverberation time: 0.88 seconds Sabine’s formula: TSabine’s formula: T60 60 = .161V/S= .161V/S Absorption coefficient of room: .09Absorption coefficient of room: .09 ART with carpets and comforter: 0.72 secondsART with carpets and comforter: 0.72 seconds

Upper Buck (cont.)Upper Buck (cont.)

Adding carpets and my comforter did not Adding carpets and my comforter did not greatly affect the spectrogram of a piano greatly affect the spectrogram of a piano chord, it only changed the reverb timechord, it only changed the reverb time

Lower BuckLower Buck

Room Characteristics: more rectangular, all walls, Room Characteristics: more rectangular, all walls, larger than UBlarger than UB

Average reverberation time: 0.44 secondsAverage reverberation time: 0.44 seconds ART with carpets and comforter: 0.42 secondsART with carpets and comforter: 0.42 seconds Absorption coefficient of room: unable to Absorption coefficient of room: unable to

measuremeasure

Individual Practice Individual Practice RoomRoom Room Characteristics: 15.6 mRoom Characteristics: 15.6 m33, small box, all , small box, all

walls, but not as smooth as upper buckwalls, but not as smooth as upper buck Average reverberation time: 0.25 secondsAverage reverberation time: 0.25 seconds Absorption coefficient of room: .265Absorption coefficient of room: .265 RT with comforter: 0.21 secondsRT with comforter: 0.21 seconds Absorption coefficient of room with Absorption coefficient of room with

comforter: .314comforter: .314

Absorption CoefficientsAbsorption Coefficients

From the data I gathered I was able to figure out From the data I gathered I was able to figure out the absorption coefficients of my comforter and the absorption coefficients of my comforter and the 3 rugs I used.the 3 rugs I used.

Absorption coefficient of my 3.5 mAbsorption coefficient of my 3.5 m22 comforter: comforter: 0.7960.796

Absorption coefficient of 3 rugs totaling 2.7 mAbsorption coefficient of 3 rugs totaling 2.7 m22 : : 0.300.30

Piano AnalysisPiano Analysis

Short C Major chord bursts of the same volume produce significantly different spectrograms in the 3 rooms

ConclusionsConclusions

Room shape, size, and types of Room shape, size, and types of surfaces present all affect surfaces present all affect reverberation times and sound qualityreverberation times and sound quality

When played on a piano, the shorter When played on a piano, the shorter RTs corresponded harsher timbresRTs corresponded harsher timbres

Individual rehearsal rooms do not need Individual rehearsal rooms do not need a long RT as there is nothing to blend a long RT as there is nothing to blend with when playing alonewith when playing alone

Higher sound quality of Upper Buck vs. Higher sound quality of Upper Buck vs. Lower Buck corresponds with Lower Buck corresponds with sentiments of my a cappella groupsentiments of my a cappella group

The EndThe End