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Posts Tagged ‘echoes’

Dead Spots – Sound System or Acoustics?

Posted by jdbsound on April 9, 2018

An unwelcomed guest in any church is Mr. Deadspots. Unfortunately, deadspots in churches are more common than you think. There are two main types of deadspots. Some are frequency related/comb filtering interference and others are dips in sound levels greater that 6dB created by the room.

It is common to see frequency related deadspots in Left/Right sound system regardless if they are Line Arrays or point and shoot speakers. These deadspots are created by interference patterns in a mono speech system as a persons voice is always mono.  These deadspots are where you shift from one foot to another and notice a sound change. In these cases it becomes a problem when on one foot you hear the highs but not the lows. When you shift your position onto the other foot, you hear the lows and the highs disappear. People with hearing aids or early stages of hearing lose notice this the most. People with good hearing notice the change too but learn quickly to put up with it. Some young people think of it as a passive noise filter. If the music is too bright, stand to one side of your seating position. If the music is too boomy, shift to the other side of your seating position. Really! Isn’t that like buying a headset and controlling the sound changes with what angle you tilt your head. It might sound like a great idea until you find yourself with a lot of neck pain. No thank you.

Sound level dips are usually acoustically related. These are created with standing waves, bass building up, hollow walls, room corners, and parallel surfaces that include walls, ceilings and floors and concaved surfaces. In all of these cases, often mid and bass energy build up and the highs are absorbed with carpets, padded pews and people. By the nature of churches and how they are used, carpeted floors and padded seating often represents how the church sounds when it is 50% full. That means that if your attendance is often over 50%, the effects of padded seating and carpeted floors has little to no impact. If church attendance is often over 70% a carpeted floor makes the room more intimate during times of prayer and solemn reverence. In the end, carpets and padded seating is a good thing.

However, because of people in the room, once that room attendance is above 50% the people absorb enough highs that extra mids and bass energy is left behind as is being amplified between parallel surfaces. This excess energy automatically masks the highs. When the highs are masked, speech and music intelligibility drops. The kicker is, if you go around the room with a sound level meter, often the sound levels don’t drop much, even when you stand in a spot where the highs (when you measure just the highs) drop off over 6dB. That is because the excess bass energy is so strong that it fools the sound meter as the meter is reading an average sound level. When you take sound level readings by frequency, then you notice the high number of deadspots in the room. Get a tone generator in a cell phone or computer app and play a constant tone at 55dB at 500 Hertz, 1000 Hertz and 3000 Hertz and then start walking around. At 500 Hertz you shouldn’t notice much of change until you get close to walls. At 1000 Hertz you will notice more changes. At 3000 Hertz, if you are hearing a lot of changes, imagine what 25% of your church audience is experiencing.

Here is a church that had both acoustical and sound system created deadspots, with a central cluster. By nature of a central cluster, in a good room, it gives the best coverage and performance for speech. There is no better way to design a church sound system unless your ceiling is less than 14 ft. high. Choice of speakers, coverage patterns and speaker placement impacts sound too but these are mainly tone qualities and gain before feedback related. It may have up to a 2 or 3% impact on overall intelligibility as well.

corner view pano Ebeneezer Church_s

In this church example, it already has a fairly good quality speaker system in the ideal location for the room. It is designed as a central cluster and by nature, in this setup, it should perform well. However, it didn’t matter if you used the main speaker system or used portable speakers on stands, with any sound amplified you could find deadspots all over the room. On top of that, if you raised your voice in the room, once you were more than 18 feet from someone, understand what was being said was difficult to impossible depending on dictions of the person talking and how good is one’s hearing. When the proper acoustical fix was applied, all of those problems went away and the church didn’t need to upgrade the speaker system.

The church decided to leave the sound system alone as the gain before feedback improved and all of the deadspots disappeared. Since this is a traditional church that has no intentions to do anything contemporary, the acoustical fix was designed to not change the overall reverb time. Before and after reverb time remained about the same. 1.7 seconds.  It was the frequency response of the room that saw a major change. As the graphs shows below, where the mixer for the worship space was located, it was also one of many spots where weird measurements were recorded before. We found dozens of spots where the room measurements went squirrely. This is typical of the results of measuring a Left/Right speaker system, not a cluster system. These weird results were a result of room acoustics and not the sound system.  We used our own test speaker for all room testing.

Sound Booth Before and After

After checking our test equipment for errors, it was then realized that by just moving the mic over a few inches, you would get a very different result. In some places, the sound was perfectly fine but move over a few inches and it was not. Our ears are about 8 inches apart. In one row of seating, the largest distance we could move the test mic between a good spot and bad spot was 14 inches. Pew seating is 18 inches.  Every seating position had both good and bad sound. What we were measuring was sound masking in the mids and lows.  The energy was so strong that it masked the highs.  Not only that but the highs were most likely also being canceled from nearby wall reflection between 1800 to 5000 Hertz.  It gave the impression that there was something wrong with the sound system.

In this church, people marked their seating positions by placing personal pillows in spots where the sound was better. Sure enough, testing these spots showed better sound before the acoustical treatment was applied. After the acoustical system was installed, the sound was the same no matter where you sat including the sound booth.

Deadspots in churches are more often a result of worship space design and not a result of sound system design (unless you have the wrong speaker system design for your room). When a church replaces a well-designed sound within 10 years, and have little to no overall improvement after an upgrade, that should be a BIG RED FLAG that you most likely have a serious acoustical problem and no amount of money spent on the sound system can make those problems go away. Besides, these days, acoustical fixes cost less than sound system fixes. As a caveat, our experience has been this. Churches that have fixed their acoustics and then wanted on to expand their music programs, they were able to upscale their sound system with a much higher budget as they upgraded, it actually lead to better performance rather than an exchange of one set of problems for another.

Bottom line is, get your church properly tested. Have someone who knows how to properly diagnose the data, and then design your church a proper acoustical management system. Install the acoustical system and watch the congregation respond and grow. Don’t be surprised if other churches want to use your church for musical and recording events. Your property value may go up too.

Note – The acoustical system is made up of 8 and 12 inch half round plaster covered foam diffusers on 3 walls.  The side walls use a gradient pattern to maximize room performance. On the back wall there are 24 units of 7 ft. x 2 ft. x 18 inch plaster covered foam diffusers that are hollow which allows for additional passive room equalizing in the near future. Project completed by church members.

By Joseph De Buglio
JdB Sound Acoustics

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Can Acoustical Spreadsheets Save Your Church Acoustics?

Posted by jdbsound on June 20, 2016

There are dozens of acoustical spreadsheets that come with the promise of a viable acoustical fix.  Some sheets are for studios and some are for home theatres.  There are also other spreadsheets for larger rooms.  As rooms get larger, (as in Christian Churches and worship centers) those spreadsheets become less accurate.  Sure, the better spreadsheets adds more variable to compensate for the limitations, but the limitations are still there. Furthermore, with all of the spreadsheets, you have to add an additional line to include a fudge factor.  In some spreadsheets you need to add multiple fudge factor lines.

When a person tries to use an acoustical spreadsheet, they are only looking at one parameter of the rooms acoustics.  You are only looking at “time.”  The problem is, for churches, and I MEAN ALL ROOMS WHERE MORE THAN 150 PEOPLE GATHER TO WORSHIP – there are other parameters that are equally or more important than “time.” Acoustical problems always come in layers.  The minimum number of layers of acoustical sound management in a worship space is 4 layers.  As a worship space becomes larger, the more layers you have to attend to.  “Time” becomes only a fraction of the real acoustical problems you are faced with.  Obviously you can’t see them but you can measure them if you are trained to recognize when you hear them.

Romanian Church Kitchener Ontario Pano 1.jpgThe problem with spreadsheets is that they are not looking issues such as standing waves – and every church – regardless of shape has standing waves (unless the space is acoustically managed in the first place which also means this article is not for you.)  Spreadsheets are not looking at excessive noise from early and late reflections.  They are not looking at bass buildup often found in the corners of a room.  They are not looking at flutter echoes and full syllable echoes.  These are all sound effects than can’t be dialed out with equalizers, delays, algorithms and the next miracle digital gadget or software. (Yet that is how most sound system designers try to deal with room acoustics.)

Regardless of a persons acoustical training, knowledge or experience,  a spreadsheet cannot tell you when standing waves are masking flutter echoes.  A spreadsheet cannot tell you when bass build up is masking a standing wave issue.  A spreadsheet can’t tell you how much the early and later reflections are reducing music and speech intelligibility. 

All that a spreadsheet can tell you is how much “time” it takes for a sound to decay in a room either as an average number.  Some spreadsheets are much more detailed and they have been written as an attempt to calculate a room in octaves or by 1/3rd octaves.  If it was only that easy.  Measuring and calculating time is just a sliver of the acoustical signature of a space people worship in. 

church of our lady small.jpg

It takes a lot of training to learn Church acoustics.  The same applies to Studio Acoustics, Recital Halls, Concert halls and lecture halls.  All of these rooms have specific acoustical needs and they all require a unique set of skills to properly fix them.   

What makes a church so complicated is in how a church is used.  When a church is designed as a “church,” it becomes the most multipurpose space there is because of all the ways a worship space is used.  When you say you want the worship space to be more “Multi-Purpose” or more flexible in it use, you are actually limiting what a basic worship space is supposed to be able to do. 

At the end of the day, an acoustical spreadsheet is only a small snapshot into church acoustics.  It can’t help with congregational singing, it can’t help with a noisy stage for a praise and worship team or choir and it can’t help with drum issues or speech intelligibility. 

What often happens is with the spreadsheet, it will guide you to a solution that is based on absorption.  When an acoustical fix is based around absorption, you wind up “killing” the room for all music – especially contemporary music and congregational singing – and the masking effects of the other acoustical issues get worse.  Sure, the room sounds more tame than it was before, but the ability to understand speech is either no better than before or it has gotten worse.  Before you know it, everyone gets in ear monitors and all of the members of the worship team have to sign an insurance liability waver stating that they will not sue the church for any future health problems with hearing loss.  Seriously, is that the kind of acoustical fix you want? 

Front view of creekside church_edited-1.jpgThat is what you get when you turn to an acoustical solution based only on spreadsheet calculations.  To top it all off, the results are not much better when using computer simulation software programs.  Simulation programs only show you the results at one frequency at a time.  The computer generated image may be 3D but the patterns they show are only one frequency at a time – even when it is averaged out.  To see large room acoustics in a simulation, you need to be able to see the results in 4D.  Hologram can’t show you 4D images.  That ability hasn’t been invented yet.  You need to be able to see sound in 4 dimensions because all sounds are complex.  Every sound made on earth is a combination of wave lengths that are generated at the same time. Some parts of a sound are measured in feet and some in inches.  There is no way to visually see 100 Hertz, which is 11 ft long, and 4000 Hertz which is 3.5 inches long, at the same time in the same place yet in real life, that is what is happening with sound.  We all take sound for granted but the complexity of sound is extensive.

But doesn’t sound follow the rules of fluid dynamic and other laws of physics?  Of course it does, but only when you examine one frequency at a time and that frequency is never a pure tone.  It is always complex.  The only place you can measure and see a pure tone is in a machine like an oscilloscope and the moment you launch that sound into the air, it becomes complex.  Just as sound is complex, so are the acoustical fixes for churches. 

jdbsound test room.jpg
This is one way to test an acoustical solution before you recommend it to a church.  Have your own testing facility.  Whatever research is done in this room, it mathematical translates perfectly when it is scaled up into a larger space.

As a mantra, remember this:  for all Christian churches, acoustical problems come in layers and whatever fix you choose, it has to address all of the layers in one step – which is possible if you want an affordable fix.  There are many tools in the Acousticians Tool Box to fix a worship space. There are diffusers, resonators, traps and other devices that can address the needs of a church’s acoustics. There are also stand-alone electronic solutions that work in certain worship spaces. You need a lot of training to know which ones you need, what combinations you need and how to use them, and the last place you want to do your training and experimenting is on your customers. 

If you are doing Church Acoustics or trying to fix your own church, don’t do it as an experiment and you know it will be an experiment the moment someone in your committee say something like, “lets try this as see what happens.”  With those words, the acoustical solution is already doomed.  Experts like myself can tell you the results the second you decide to try something and long before you apply the materials. 

History shows that after a church spends it’s money on a thing such as acoustics, it will not be able to afford to fix any mistakes for decades.  If the results makes the room worse or no better than before, then you are subjecting the church members to more sound abuse for years to come and we don’t want that.  Spreadsheets don’t fix churches, good training and expert help does. (It’s also cheaper in the end to get expert help.)

Finally,  consider this.  The internet has become a treasure trove of knowledge.  That knowledge is often presented as expert information offering sure fire solutions.  I scan the internet often to see what is out there.  There is a lot of great information and there are a lot of myths.  When you collect all of that info, it only holds a fraction of the total knowledge about church acoustics.  If we were to put a percentage on it, the internet holds about 2% of the total knowledge there is for church acoustics.  The books hold another 8% of what there is to know about church acoustics.  Church acoustics is so complicated that often, a seasoned acoustical expert like myself will have to fix one of a kind acoustical fixes often.  Those unique fixes are often not shared because others may think that the one of a kind fix would be needed in every other church that has the same problem.  You can have 10 churches with the same acoustical problem but in every one the fix has to be modified because of the other variables that have to be included.  The rest of the knowledge about church acoustics is held by experts because the church community hasn’t taken ownership of that knowledge yet and there is no system in place for churches to share their experiences in order to avoid mistakes in the future.  What is missing is the wisdom in knowing what acoustical fixes will enhance worship verse what acoustical fixes exchanges one set of problems for another set of problems. Problems which holds back and undermines the real worship experience the church leaders want you to participate in. 

All church can have great acoustics and sound.  If each church denomination or independent church were to set-up their own “Church Sound Standards” for the performance of their sound systems and worships space acoustics, churches will become the kind of places where people want to go.  Once a standard is set, every church will have a Worship everyone can enjoy and appreciate. 

Joseph De Buglio
Acoustician and Expert in Church Acoustics.

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Message for Architects and New Church Buildings

Posted by jdbsound on February 19, 2015

It has been brought to my attention by a number of church members about who gets to decide the final aesthetics of worship space interiors.  Church members of some newly built churches which are less than one year old were pointing out to me that in the end, we acoustical designers get to ultimately decide the final aesthetics of a church – not the architect, no matter how much effort an Architect puts into the aesthetics of a worship space.   If this sounds familiar then check out my post in 2012 where I made a similar post.  This discussion comes up often.

It seems that when acoustics are included in the design stage of a worship space, the Architect has the last say on the rooms aesthetics – assuming the acoustical plans are not compromised later on.  When acoustics are left out of the design phase of planning a new church, it is people like me that get the final say in the room aesthetics. Whether it is while the building is being built or anytime later – even 200 years later, it is people such as myself that often make the final aesthetic changes that will last the life time of a church building. 

The good news is, is that when we are included in the design phase of a new church, often our acoustical designs blend into the architecture and it is often not seen or at least not seen as an acoustical add-on.  In fact, often our acoustical designs come off as the Architects design of the worship space and at times to the untrained person it looks like we had done nothing.   Where friction often comes up, is when after the design of the church has been completed and the church board has given the green light, that is when someone raises the issue of acoustics.  Often there are major acoustical issues as what is taught in Architectural schools is about concert hall acoustics, school auditorium acoustics and lecture room acoustics. 

Church acoustics is totally different and I don’t know of any place were “church acoustics” is taught.  This is often why bringing someone like me after a finished design is presented to a church where butting heads starts.  When there are glaring mistakes being made and we point them out, it often means major design changes which often cost money to change at this phase.  Once past the design phase, churches are rarely ready to pay for design changes that often means delaying the project which increases costs higher.  As a result acoustics is usually left until the church is finished.  But wait!  A church is not finished until the acoustics are done.

As stated before, it is people like me who get to decide the aesthetics of a church when acoustical design is left out.  This goes for new churches, storefront churches, churches moving into commercial buildings or are using commercial building designs and churches doing renovations.  If you are an architect, include us at the beginning of the design process and the aesthetics will be all about you.  Leave us out of the design process and no matter how beautiful a space you thought you designed, it will be people like me who get to decide it’s final finish and sometimes, what we do is not very flattering but when it sounds great, the less than pleasing acoustical treatment starts to look good. 

Joseph De Buglio  

PS: Don’t call us if you want someone to just rubber stamp your worship space designs.   

  

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