Table 2. Prioritized recommendations for sound system enhancements and acoustical finishes. PRIORITY SOUND SYSTEM ACOUSTICAL FINISHES Scheme 1: Priority 1 Priority 1: Rear Surface Treatment to Reduce Acoustical Defects Provide sound absorbent material on the rear ceiling area of the Sanctuary (Priority 1: Item 1) 1 Provide sound absorbent material on the wall surfaces at the rear Provide new column corners of the Sanctuary. array loudspeakers o Rear glass wall (Priority 1: Item 2) o Rear HVAC columns (Priority 1: Item 3) o Side gypsum board wall (Priority 1: Item 4) Scheme 1 Alt. Priority 1: Rear Surface Treatment to Reduce Acoustical Defects Provide sound absorbent material on the rear ceiling area of the 1 Alt. 2 3 3 Alt. 4 If funds do not allow purchase of new loudspeakers, re-aim and relocate the existing loudspeakers Scheme 2: Priority 2 Re-aim and relocate the existing speakers as fill loudspeakers (in addition to column array loudspeakers) Sanctuary (Priority 1: Item 1) Provide sound absorbent material on the wall surfaces at the rear corners of the Sanctuary. o Rear glass wall (Priority 1: Item 2) o Rear HVAC columns (Priority 1: Item 3) o Side gypsum board wall (Priority 1: Item 4) Provide sound absorbent material on the front-facing column surfaces of the three rear-most HVAC columns. (Priority 1: Item 5) Priority 2: Ceiling Treatment Options to Reduce Acoustical Defects A) Provide sound absorbent B) Provide concave-curved material in the center part of diffusing panels in the center the rear ceiling area: portion of the ceiling area: -This will help to reduce acoustical -This will help to scatter harsh sound defects including echoes and harsh reflections and help to reduce sound sound reflection to increase speech focusing caused by the shape of the intelligibility. ceiling planes without reducing -This would cause the Sanctuary to reverberation in the room. be more dead for the organ and traditional music. (Priority 2: Item A) (Priority 2: Item B) Priority 3: Side Wall Treatment Options to Reduce Acoustical Defects A) Provide sound absorbent B) Provide sound diffusing treatment on 40-60% of the elements along the rear half of rear half of side wall glass side wall glass windows: windows: -Strategically placed absorption will -This will help to scatter sound help to reduce harsh sound reflections that strike the windows and reflections from side windows. This help to reduce harsh sound reflections would cause the Sanctuary to be while maintaining the reverberation in more dead for the organ and the space for the traditional music traditional music. (Priority 3: Item A) (Priority 3: Item B) Priority 3: Side Wall Treatment to Fine Tune the Space Provide variable acoustic treatment at side wall glass: retractable banners in front of side wall glass windows -This will reduce reverberation for contemporary music and will help to reduce any harsh sound reflections from the windows when deployed. (Priority 3 - Alternate) Priority 4: Rear Narthex Wall Treatment to Fine Tune the Space Replace the sound absorption on the rear Narthex wall to help reduce a broader range of sound frequencies. (Priority 4) S A S i e b e i n A s s o c i a t e s, I n c. P a g e 8
CONCEPTUAL SOUND SYSTEM ENHANCEMENTS There are 2 schemes provided to improve the coverage of the congregational seating area by the loudspeaker system and to reduce the extent to which amplified sounds strike and reflect off the room surfaces. Providing uniform coverage of the congregational seating area and reducing the spill of amplified sounds onto wall and ceiling surfaces are essential to optimize the clarity and intelligibility of the spoken word. Scheme 1 consists of purchasing and installing new digitally steerable column array loudspeakers to be located at the front of the Church. Sometimes the use of these loudspeakers can achieve high levels of speech intelligibility in rooms without much additional acoustical treatment. Scheme 1 Alt. consists of relocating and re-aiming the existing loudspeakers to provide more uniform sound levels across the congregational seating area. Scheme 2 consists of purchasing 2 new digitally steerable column arrays that will be mounted on vertical surfaces on both sides of the platform and relocating the existing loudspeakers to function as fill speakers towards the rear of the room. This scheme will have the added advantage of providing both uniform sound levels in the congregational seating area and not having amplified sounds striking significant areas of the room surfaces. Please note that these schemes are conceptual recommendations per our scope of work. Detailed analysis, computer modeling and providing bid documents based on the selected scheme would be additional services. We would be pleased to work with you in this regard. SCHEME 1 Purchase new column array loudspeakers and mount them on vertical surfaces on the platform. These surfaces will be somewhere between 8 up to 2 feet or 4 feet wide by at least 10-6 tall made of wood to match the existing wood surfaces in the choir area, as shown in Figures 5 and 6. This scheme will involve purchasing the new column array loudspeakers, constructing the vertical elements shown on the drawings on which to mount them, running new wires to the loudspeakers and providing 120 volt power at the location of the new powered loudspeakers. In addition, new wires to connect the relocated existing loudspeakers with the existing amplifiers and processor, adding new suspension hardware to relocate the existing loudspeakers in the positions shown in the drawings and adjusting the processor controls to reset the delays and other processing functions for each loudspeaker. The approximate budget cost for the new column array loudspeaker system is $35,000.00 to $55,000.00. Manufacturer s representatives may provide demonstrations of the loudspeakers if requested. We would be pleased to assist in arranging a demonstration if desired. A. Scheme 1A includes six (6) Bose MSA12X column array loudspeakers used in conjunction with relocated ceiling speakers. These are steerable column arrays so that the coverage patterns can be adjusted to provide amplified sounds to the desired audience area and reduce sound from spilling up onto rear wall and ceiling surfaces of the Sanctuary. B. Scheme 1B includes two (2) Renkus Heinz IC16-RN column array loudspeakers used in conjunction with relocated ceiling speakers. These are also steerable column arrays so that the coverage patterns can be adjusted to provide amplified sounds to the desired audience area and reduce sound from spilling up onto rear wall and ceiling surfaces of the Sanctuary. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 9
SCHEME 1 ALT. Relocate and re-aim the existing loudspeakers in the room as shown in Figures 3 and 4. This will involve adding new wires to connect the loudspeakers with the existing amplifiers and processor, adding new suspension hardware to locate the loudspeakers in the positions shown in the drawings and adjusting the processor controls to reset the delays and other processing functions for each loudspeaker. Three-dimensional computer modeling and analysis would be required to determine recommended angles and optimized location for the loudspeakers which would be additional services. SCHEME 2 1. Priority 1: Purchase new column array loudspeakers and mount them on vertical surfaces on the platform as discussed in Scheme 1. 2. Priority 2: Move and re-aim existing Bose LT6403 loudspeakers to use as rear fills if needed. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 10
Figure 3: Plan mark-up showing Scheme 1 Alt loudspeaker locations. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 11
Figure 4: Section mark-up showing relocated and aimed Scheme 1 Alt existing loudspeaker locations. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 12
Figure 5: Plan mark-up showing Scheme 1 Priority 1 and Scheme 2 Priority 2 loudspeaker locations. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 13
Figure 6: Section and photo mark-up showing Scheme 1 Priority 1 and Scheme 2 Priority 2 loudspeaker locations. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 14
ACOUSTICAL MEASUREMENTS AND ANALYSIS There are 3 ways to quantitatively assess the reflective and reverberant acoustical environment in spaces: 1. Impulse Response 2. Reverberation Time 3. Average absorption coefficient or Alpha Bar Two sets of impulse response measurements and reverberation time measurements were conducted in the Sanctuary. One set of measurements was conducted with the space excited with a simulated natural acoustic sound source. The second set of measurements was conducted with the space excited through the house sound system. The natural acoustic sound source was located in center of the raised platform where natural acoustic sources, such as the pastor speaking, would be located. Impulse responses and reverberation time measurements were obtained with a laptop computer using WinMLS software that produces a maximum length sequence signal that was played through a JBL EON615 loudspeaker placed at standing head height above the finish floor simulating a natural acoustic sound source and then played through the existing sound system in the Sanctuary consisting of four Bose LT6403 loudspeakers and four Bose LT6400 loudspeakers. The source sound is received by an Earthworks microphone connected to a Digigram VX Pocket V2 End User sound card input in the computer. The signal is processed on a laptop computer using WinMLS software to calculate acoustical measurements. The microphone was mounted on a stand approximately 42" (seated ear height) above the floor and was placed at 12 different receiver locations throughout the Sanctuary. Average absorption coefficients were calculated based on the reverberation time measurements. The measurement and calculation methods and the results are discussed below. IMPULSE RESPONSES An impulse response is an acoustical measurement that shows the amplitude or loudness and the arrival time of the direct sound and each reflected sound in the room from unique paths between the sound source and the receiver. The direct sound is the sound that travels from the pastor, musicians or loudspeakers to a congregant seated in the Sanctuary through the air without striking any of the room surfaces. Reflected sound propagates from the person speaking or musical instruments playing, which then strikes the wall and ceiling surfaces and reflect to the listener. Ideally, the amplitudes of the reflections should decrease with time without large spikes of delayed sound reflections. However, many of the impulse responses measured in the Sanctuary showed an uneven, prolonged decay of sound, and harsh sound reflections and echoes caused by hard, sound reflective wall and ceiling surfaces. A series of high amplitude sound reflections, or spikes can be seen in the impulse response after the direct sound in Figures 1 and 2. These sound reflections are caused by the ceiling, windows, hard walls, and rear corners of the room. These repeated harsh sound reflections decrease the clarity of sound at listening locations. When the reflections strike one or more room surfaces repeatedly, they cause excessive reverberation which decreases the clarity of speech and music. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 3
The impulse response in Figure 1 shows the direct sound and the decay of reflected sounds in the Sanctuary in the 1000 Hz (mid-frequency) octave band measured with the microphone receiver located in the center of Row K in the far-right seating section using the simulated natural sound source located on the raised platform. The impulse response shows scattered reflections from multiple surfaces including the glass walls, the forward-facing side of the HVAC columns, and the rear ceiling surfaces that cause an uneven decay of sound. Delayed, harsh sound reflections from the rear back corner of the Sanctuary that are heard as an echo are also shown in Figure 1. Other impulse responses measured at locations throughout the Sanctuary with the simulated natural sound source located on the raised platform showed similar harsh sound reflections and echoes. Figure 1. Impulse response measured in the center of Row K in the far-right seating section with a simulated natural acoustic sound source located in the center of the raised platform. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 4
The impulse response in Figure 2 shows the direct sound and the decay of reflected sounds in the Sanctuary in the 1000 Hz (mid-frequency) octave band measured with the microphone receiver located in the center of Row K in the center-right seating section using the existing house sound system as the source. The impulse response shows harsh reflections originating from multiple loudspeakers striking the angled ceiling surfaces. Also, delayed reflections heard as echoes from multiple surfaces in the rear corners of the space including the glass walls, angled walls, and gypsum board walls are shown. Other impulse responses measured at locations throughout the Sanctuary using the existing house sound system as the source showed similar harsh sound reflections and echoes. Figure 2. Impulse response measured in the center of Row K in the center-right seating section using the house sound system as a source. Treating the angled ceiling surfaces in the rear half of the space and the available rear and side wall with sound absorbent material as discussed below will help to reduce the harsh sound reflections, echoes and excessive reverberation in the room. This should be done in conjunction with sound system enhancements including adjusting the aiming and location of the existing loudspeakers or providing new steerable array column loudspeaker systems for the Sanctuary with careful aiming sound system to help reduce the amount of sound that will strike the hard ceiling and wall surfaces in the Sanctuary. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 5
REVERBERATION TIME Reverberation is the prolonging of sound in a room after the source has stopped due to repeated reflections from the room surfaces. Reverberation time (RT) is the amount of time (usually measured in seconds) it takes for sound to decay 60 db after the source has stopped. The 60 db decay that is measured is how much the sound level drops until it becomes part of the background sound. Reverberation time is controlled by the amount of sound absorbing material in a room and the volume of the room. The results of the reverberation time measurements are summarized in Table 1. Table 1. Average reverberation times (RT) measured in the Sanctuary. Average Reverberation Time (seconds) Sound Source Simulated Natural Sound Source Located on the Raised Platform Octave Band Center Frequencies (Hz) 63 125 250 500 1000 2000 4000 8000 Mid- Frequency Average 3.5 3.9 3.5 2.9 2.6 2.3 2.0 1.4 2.8 Existing House Sound System 4.0 3.9 3.5 3.0 2.7 2.3 1.9 1.4 2.8 Mid-Frequencies The unoccupied average reverberation times in the mid-frequencies are 2.6 to 3.0 seconds for the Sanctuary. The recommended reverberation times for churches with natural acoustics with choral and organ music are between 1.9 to 2.6 seconds. The prolonged reverberation times in the Sanctuary are generally suitable for the traditional, liturgical music, but are excessive for amplified music and speech. Also, the reverberation times in the Sanctuary are caused by sound reflecting multiple times off the wall and ceiling surfaces that create acoustical defects including sound focusing and harsh, delayed sound reflections rather than enhance the sound in the Sanctuary. Therefore, harsh sound reflections and echoes should be reduced to the extent possible given the physical geometric constraints of the room by providing a combination of sound absorbent material on available ceiling and wall surfaces and by providing sound system enhancements and sound diffusing materials to directing the sound away from hard surfaces as discussed in the section below. The Acoustical Finish Recommendation section includes prioritized recommendations for finishes that will help to reduce the acoustical issues in the Sanctuary. With the addition of the Priority 1 acoustical treatment discussed below, the estimated reverberation time in the mid-frequencies will be approximately 2.1 to 2.4 seconds in the Sanctuary. Further addition of sound absorbent materials in the Sanctuary may cause the room to be considered too dead the organ and choral music. Both sound absorbent material options and sound diffusing material options are included for the Priority 2 and 3 recommendations depending on the acoustical preference of the Church Staff and congregation. The addition of sound diffusing materials will not affect the reverberation time in the Sanctuary. With the addition of the Priority 1 recommendations and the Priority 2 sound absorbent treatment options, the estimated reverberation time in the midfrequencies will be approximately 1.6 to 1.8 seconds in the Sanctuary. With the addition of the Priority 1 recommendations and the Priority 2 and Priority 3 sound absorbent treatment options, the estimated reverberation time in the mid-frequencies will be approximately 1.6 to 1.7 seconds in the Sanctuary. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 6
AVERAGE ABSORPTION COEFFICIENTS OR ALPHA BAR The average absorption coefficient or alpha bar for the room is the average amount that the room surfaces absorb sound each time a sound wave strikes them. An alpha bar of 0.10 means that on average 10% of the sound striking room surfaces is absorbed and 90% is reflected back into the room. An alpha bar of 0.20 is the usual break point between an acoustically live room that amplifies or reinforces sounds by reflections from room surfaces and one that is acoustically dead or begins to absorb sounds made in the room. To reduce excessive reverberant noise levels and to improve the clarity of amplified sounds, a slightly absorbent room is recommended. Therefore, an alpha bar of 0.20 to 0.30 is recommended for the Sanctuary This means that on average 20% to 30% of the sound is absorbed each time it strikes room surfaces and 70% to 80% is reflected back into the room. The current alpha bar in the Sanctuary is approximately 0.18 to 0.22 in the mid-frequencies. When there is not enough absorption in the room and sounds reflect off multiple surfaces, amplified sounds become muddy, and clarity of music and intelligibility of speech can significantly decrease. With the addition of the Priority 1 acoustical finish recommendations, the average sound absorption coefficient will increase to approximately 0.26 to 0.30 in the mid-frequencies. Further increasing the alpha bar in the Sanctuary may deaden the room. With the addition of the Priority 1 recommendations and the Priority 2 sound absorbent treatment options, the average sound absorption coefficient will increase to approximately 0.35 to 0.38 in the mid-frequencies. With the addition of the Priority 1 recommendations and the Priority 2 and Priority 3 sound absorbent treatment options, average sound absorption coefficient will increase to approximately 0.35 to 0.39 in the midfrequencies. ACOUSTICAL DESIGN RECOMMENDATIONS The position and aiming of the existing loudspeakers, the hard, reflective wall and ceiling surfaces, and the unique geometry of the Sanctuary all contribute to the acoustical issues that are currently experienced in the Sanctuary. Conceptual recommendations for sound system enhancements and for acoustical finishes are included in Table 2. The recommendations are grouped and ordered into tasks to provide improvements in the intelligibility of the spoken word, the clarity of music, and excessive reverberation with the implementation of each phase of the recommendations. While all of the following items may be implemented to provide an optimal improvement, the recommendations are listed in the order of priority that they should be implemented in if costs are limited and it is desired to approach the recommendations in phases. Also, alternate sound system schemes and acoustical finish options that may be suitable given the budget and acoustical preferences of the Church Staff and congregation. Detailed descriptions of each recommendation scheme or option are included in the Conceptual Sound System Enhancement section and Acoustical Finish Recommendations section following Table 2. The priority and item number listed for the acoustical finishes corresponds to the detailed description for that recommendation that is included in the Acoustical Finish Recommendations section. S A S i e b e i n A s s o c i a t e s, I n c. P a g e 7