aINSTRUMENTAL PLANNING GUIDE FOR NEW
Introduction
Every year music teachers are subjected to low pressure waves – aka “noise” – or loudness sufficient to cause permanent hearing loss. The term that has been coined for this condition is Noise Induced Hearing Loss or “NIHL”.
In 2012 the National Institute for Occupational Safety and Health (NIOSH) produced a Health Hazard Evaluation Report at the request of an employee concerned about hearing loss from loud noise exposures during music classes and band rehearsal (NIOSH 2012). Consistent with previous studies, the evaluators found that the Recommended Exposure Limit (REL) exceeded the occupational exposure limits promulgated by NIOSH and OSHA.
Based on this evaluation NIOSH made six (6) recommendations; the first of which was to “hold marching band rehearsal outside or in a room appropriately sized for the number of band students,” and “If marching band rehearsal must take place in the (inadequately sized) band room, all students should be asked to play softly and focus on technique. . ..”
(What’s the fun in playing softly? How shall a musician practice for a performance in space designed for soft focus on technique?
Something about music / heart / brain connection . . .For students, we ask, where’s the fun in that?)
The information presented in this guide is intended to familiarize Architects, Educators, and Administrators, involved in the design of music education facilities, with best practices and baseline (minimum) criteria for developing a successful band room project that is ear (hearing) friendly (safe?), FUN and acoustically appropriate.
The main areas of focus are:
1) Programming for volume
2) Room Ratios
3) Application of wall, ceiling and floor treatments
4) Methods for altering room modes
5) Tips & tricks for aesthetically appealing solutions
Programming for Volume
Cubic volume is strong predictor of acoustical quality & project success.
Existing guidelines recommend ceiling heights of 16 – 22 feet and a floor area ranging from 25 – 35 sq. ft. per instrumentalist to account for a wide range of seating configurations, reverberations times. And while a heavy emphasis is placed on cubic volume, current programming methods have failed to address the industry standard of dollar per square foot construction estimating.
In response to the construction industry standard of estimating building cost on a dollar per sq. ft. basis; as such, it is not uncommon for rehearsal rooms to be programmed on the lower end of the recommended floor area range. This practice runs the risk of failing to address two crucial items:
1. Occasional, temporary, and long term population adjustments.
2. Construction constraints associated with working inside, or adjoining an existing structure
To address these conflicts, we have developed an innovative tool . . . .
We will review this tool and subsequent criteria in the follow two Programming Studies
Study #1 – Square Foot per Instrumentalist Programming Method
1200 sq. ft. room for 45-50 instrumentalists
Square Foot per Instrumentalist: 24 – 26.6 sq. ft.
Ceiling Height: Undetermined
Constructed to meet the minimum recommended volume, and appropriate “voice” or reverberation time; a 1200 sf room for 45 – 50 persons would require a minimum ceiling height 16’-0”.
Increase the student population by 10 students, and the effective floor area is reduced to 20 sq. ft. per student; volume is reduced to 320 cu. ft. per person. The same 1200sf rehearsal room designed to achieve an “ideal” volume would have greater capacity to accommodate shifting student populations and occasional increases in ensemble size; however, the necessary ceiling height may be unachievable. A 1200sf room design for 45-50 persons with an ideal volume of 600-700 cu. ft. a person would require a ceiling height exceeding 24’-0”
As an alternative to a starting with a sq. ft. per instrumentalist calculation, use the chart below to quickly identifying the minimum sq. ft. per instrumentalist based on a guesstimate of the reasonably achievable ceiling height for your specific project. A guesstimate for this exercise is all that is required as this chart is designed to illustrate and appropriate volumetric range
This chart is set to provide a reverberation time of .9 – 1.1 in a rectangular rehearsal room when an average wall treatment rate of 50% is applied to all walls. The recommended reverberation times are applicable to band and orchestra rehearsal. Woodwind, choral rehearsal rooms, and performance spaces have different recommended reverberation times.
Study #2 – Volumetric Programing Method
1200 sq. ft. room for 45-50 instrumentalists
Square Foot per Instrumentalist: To Be Determined using the Volumetric Ratio Chart
Ceiling Height: Existing Construction
For example: If the height of your rehearsal space will be determined by aligning with an existing structure having a 12’-0” floor-to-floor / floor-to-roof height, or a 24’-0” nominal bldg. height, by subtracting approximately 5’-0” for structure & mechanical ductwork you may assume your ceiling height will not exceed 19’-0”. An acceptable or good room volume may be achieved at 25 sq. ft. per person, however an ideal room volume will require approximately 32 sq. ft. per person.
In the same fashion, if you are programming a new project from ground-up, and can reasonably expect to achieve a minimum ceiling height of 22’-0”, a floor area of only 28 sq. ft. per person will be necessary to achieve a “very good” to “ideal” room volume.
In short, the smaller the floor area, the greater the ceiling height required to dissipate the sound pressure waves or “loudness.”
Upon determining the base floor area, increase the sf per person as desired to accommodate specific seating arrangements, instrumental groups, or instrument storage.
FIGURE 01 – ROOM RATIO
THE PREFERRED LENGTH TO WIDTH RATIO FOR THE TRADITIONAL RECTANGULAR REHEARSAL ROOM IS APPROXIMATELY TO A X (A + 1/3A). WHEN CONFIGURING A REHEARSAL ROOM BE CAREFUL TO AVOID SQAURE ROOMS OR LONG NARROW ROOMS AS THESE CONFIGURATIONS CAN CREATE UNDESIRABLE ECHOS AND INEFFICIENT USE PATTERNS RESPECTIVELY.
Application of Wall, Ceiling & Floor Treatments
Flooring: Provide a low pile carpet without any additional cushioning
Ceiling: Provide a fiberglass ceiling with a minimum STC rating of 1.0
Walls:
FIGURE 01
TREAT THE “FRONT” OF THE ROOM WITH SOUND ABSORBING PANELS. THIS IS THE WALL THAT INSTRUMENTALISTS WILL FACE WHEN PLAYING THEIR INSTRUMENT. NOTE: THIS WALL MAY OR MAY NOT BE THE SAME AS THE TEACHING WALL. REFERENCE FIGURE “XX” METHODS FOR ALTERING ROOM MODES FOR ALTERNATE ROOM CONFIGURATIONS.
FIGURE 02
TREAT THE WALL OPPOSITE THE “FRONT” WALL WITH A MIXTURE OF SOUND ABSORBING AND SOUND DIFFUSING PRODUCTS. INSTALLATION PATTERN SHALL BE DESIGNED TO ELIMINATE OR SIGNIFICANTLY RESTRICT PARALLELL REFLECTIVE SURFACES BY LOCATING DIFFUSERS / ABSORBERS DIRECTLY ACROSS FROM UN-TREATED WALL SURFACES.
APPLY THE SAME TREATMENT METHOD TO THE SIDE WALLS TO ELIM
METHODS FOR ALTERING ROOM MODES
FIGURE 04
LOCATING INSTRUMENTAL STORAGE WITHIN THE INSTRUMENTAL ROOM CAN BE A COST EFFECTIVE METHOD FOR MODIFYING THE ROOM MODE OR “RESONANCE”. PROVIDE INSTRUMENT STORAGE WITH GRILLE TYPE DOORS. SPECIFY CABINETS WITH AN ACOUSTICAL BACK IF ADDITIONAL ABSORPTION IS DESIRED. THE ABSORPTION PROVIDED BY ACOUSTICAL STORAGE CABINETS SHOULD BE COUNTED IN THE OVERALL RATIO OF DIFFUSION TO ABSORPTION WITHIN THE ROOM.
FIGURE 05
ALTERNATE CONFIGURATIONS CONSISTING OF SPLAYED OR ANGLED WALLS WILL ALTER THE ROOM MODE; HOWEVER THE REDUCTION OF USEABLE FLOOR SPACE AND INCREASED COST OF CONSTRUCTION ARE NOT TYPICALLY WORTHWHILE OR NECESSARY TO ACHIEVE AN ACOUSTICALLY APPROPRIATE.
FIGURE 06A AND 06B – TREATMENT ZONES