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Posts Tagged ‘Church sound’

1 + 1 = 3 or When is Doubling the Power, not +3dB?

Posted by jdbsound on June 17, 2019

Here is a simple test anyone can do to determine the acoustical condition of a church.  Physics says that when the power* is doubled or when doubling the number of speakers, the sound level will increase 3dB.  This result is real when outdoors.  This outcome can be false indoors.  When it is false indoors, it is because there are acoustical problems.  Please notice that it is problems, not a problem.  When adding a second speaker failing to increase the sound 3dB, this test shows that it is never a single acoustical issue.  It is not a sound system problem.  The sound system is exposing the root problem. (If the second speaker is wired out of phase, the sound will decrease in level.)

Outdoors, sound follows the basic rules of physics.

When outdoors, if there are two loudspeaker playing with the same volume of pink noise side by side or up to 6 feet apart, and set up a test microphone or SPL meter 30 feet away. (An iPad or phone with testing software can be used if it is calibrated.) When the second speaker is turned on or off,  the sound level will change 3dB.  This result is constant in physics.  The reason this is always true is that there are no barriers around to limit the sounds from spreading out or returning from a reflection that can interfere with the direct sound.

When indoors, depending on the size of the room, often this is not true.  This failure is noticed the most with Subs and sound energy below 500 Hertz.  Doing the same test at 30 feet inside of a church, the sound level change is often 1, 1.5, or 2dB.  If the result is 3dB, there are either a lot of open windows, lots of doors that are open, the church has more than 3000 seating or the church has great acoustics. 

Indoors, sound is confronted with many other rules of physics which changes how the first rule works.

Here are the most common reasons for the sound failing to increase 3dB when doubling the power or speakers.

  • Standing waves
  • Dimensions of the room
  • Too much-stored energy in the corners
  • Too much high-frequency absorption

Standing Waves

Standing waves are excessive amounts of energy between parallel walls within a confined space.  It can often hear it.  To listen to it in a rectangle room, go between the parallels walls that are the closest together. Often it is the side walls.  Stand about 4 feet from one of the side walls.  Make a loud, sharp noise like a hand clap once.  If a person hears any rapid pinging sounds, this is a sign of standing waves.  The sound heard is often a higher range of frequencies, and they usually called flutter echoes.  Flutter echoes are a symptom of standing waves.  Bass sounds, which have longer wavelengths can’t produce the same volume of sound to hear as a flutter between parallel walls.  Whenever a person hears flutter echoes, excess bass energy present too.  This result is also true for all other room shapes when flutter echoes or flutters from a simple hand clap occur.

A second clue to standing waves is when standing at a pulpit or where a minister preaches from. With a hand clap, if the reflected sounds are coming from the side walls or behind standing waves are the cause of it.  The standing waves are preventing a large portion of the sound from reaching the other side of the room, and what is reflected back is being canceled out by the standing waves a second time which in turn prevents people from hearing the clapping returning from the back of the room. Standing waves have the effect of isolating everyone from each other in the room.  This result is also why the drummer seems to sound so loud and why most drummers strike the drums harder than they have too. It is because they can’t hear their drums at a lower level.  This outcome is also why many people comment that they can’t hear themselves when singing, and it makes them feel alone in a room full of people.

Any church with parallel walls will have standing waves if there is nothing to manage them

The reason the sound doesn’t increase 3dB when adding a second loudspeaker is because of the excess bass energy created by the standing waves in the worship space.  The excess air pressure is like putting a finger lightly on the woofer.  The excess air pressure acts as an acoustical load on the woofer, and that dampens the amount of sound coming from the loudspeaker.

Standing waves can only be removed with diffusion or some form of sound scattering. 

If people try to use absorption to fix this problem, while it will remove the flutter or in some cases, shift the flutters to a lower frequency, the untreated bass energy will make the standing wave problem more pronounced.  It will increase the feeling loneliness and discourage the congregation from singing even more.

The dimensions of the room

In churches with low ceilings or seating less than 200 people, the room is too small to be free from surface related sound inference reflections.  In a larger church space with a flat ceiling less than 16 feet high, the room will have standing waves floor to ceiling which limits the ability to increase sound 3dB with just doubling the speakers.

The reason the sound doesn’t increase 3dB when adding a second loudspeaker is that the room is limiting how much the space can support.  The excess air pressure from the extra speaker is like putting a finger lightly on the woofer.  The excess air pressure acts as an acoustical load on the woofer, and that dampens the amount of sound coming from the loudspeaker.

The only option is to diffuse all of the room if a small church.  If a low ceiling, diffusers will have to be added to the ceiling.  Acoustical tiles and drop ceilings cannot correct this issue.

Too much-stored energy in the corners

Another principal of physic is how sound is affected by boundaries.  A loudspeaker on a 10-foot pole measures 60dB.  We call that free space.  When we put the speaker on the ground, the speaker will be 6dB louder.  That is referred to as “half space.”  When we add a wall and the floor, we call that “1/4er space” and the sound increases 12dB or doubles in loudness.  When we add a second wall to the floor and create a corner, that is “1/8th space,” and the sound rises 18dB. 

Corners collect the air pressure that is created by longer wavelength sounds that accumulate on the flat surface of the wall.  With nothing to direct the sound, the sound pressure moves in all directions.  Eventually, the excess bass energy makes its way to the corners.  Depending on a lot of variables, the amount of energy that builds up is often too much.  Churches will low ceilings, large flat walls, or flat ceilings tend to have too much excess bass in the corners.  All other church shapes, except for domes have varying levels of corner issues if not managed.  Excess corn energy has a similar effect as standing waves.  When there is too much bass, it masks the highs.  This, in turn, creates hotspots and coldspots throughout the room. Hotspots and Coldspots are frequency dependent. If the sound level changes are of a narrow range of frequencies, it was most likely found them with instruments.  When a person notices them with their ears,  it means anyone with a hearing problem will miss out on some of what is being said, or what they heard and what was said was different. 

When the front of a church is in the corner, everything is either 18dB louder or 18dB quieter when compared with churches that have the front on an end wall.

The reason the sound doesn’t increase 3dB when adding a second loudspeaker is because of the excess bass energy created by the bare walls in the worship space.  The excess air pressure is like putting a finger lightly on the woofer.  The excess air pressure acts as an acoustical load on the woofer, and that dampens the amount of sound coming from the loudspeaker.

Keeping excess sound out of the corners is best done with diffusion.  It cannot be done with absorption unless the absorbers are as thick as the wavelength of the sound waves.

Too much high-frequency absorption

Sound arrives at our ears as air pressure vibrating at a rapid rate.  The faster the air vibrates, the higher the sound pitch.  The slower the sound vibrates, the lower the pitch. The vibrations are referred to as Hertz.  Sound travel at 1130 feet per second.  At 100 Hertz, a bass sound has the wavelength of just over 11.3 feet.  At 1,000 Hertz the sound waves are 1.13 feet, and at 10,000 Hertz the sound waves are 0.11 feet or 1.3 inches.  

When there is too much absorption in the room, what is left is too much bass. The excess bass masks the highs. 

For most churches, carpeted floors and padded seating is all the absorption needed. When this much absorption is add, the congregational singing is very dull and people have to be super motivated to see more that 20% of the audience singing.

The reason the sound doesn’t increase 3dB when adding a second loudspeaker is because of the excess bass energy created by too much absorption.  The excess air pressure is like putting a finger lightly on the woofer.  The excess air pressure acts as an acoustical load on the woofer, and that dampens the amount of sound coming from the loudspeaker.

The fix for such a problem is by removing the right amount of absorption panels and replace them with diffusers.  Then complete the room by adding more diffusion throughout the sanctuary to correct the frequency response of the room.

These four issues are never a singular issue.  They are often in combinations or can include all four.  Along with these problems, there are often reverberation issues, echoes, excess late reflections, the poor frequency response of the room, and other room problems that have little to do with this simple 3dB test, but they are usually there as well.  These problems can be heard when a person learns what to listen for.  Looking at how sound system is equalized is another clue of room problems.  The issues have the result of the high numbers of the congregation not singing. (In a church with good acoustics, they will often have more than 80% of the congregation singing every they are familiar with.)

Getting two loudspeakers and doing this test is simple and easy to do.  If the sound doesn’t increase 3dB, this means that adding more subs or more speakers into a worship space will not get the expected outcome. For example.  If the goal is to increase the bass in a worship space 3dB, and sound system has only one subwoofer, do this test, If the bass increased only 1.5dB with the second box, then it will take two more speakers just to get a 3dB increase for a total of 4 boxes. Think of the cost of adding three speaker boxes and all of the related hardware required to support that.  An alternative would be to fix the room with diffusion, the gain will be 6 to 10dB of performance without doing anything to the sound system.  It would be equal to adding 8 or 16 subwoofers depending on other acoustical or architectural considerations.  

Science is amazing when appropriately used to provide real solutions. Pseudo-Science or fake data is often used under the disguise of science and can be used to lead churches to false conclusions.  Many experts in audio and acoustics who see the same data, know these problems are present.  If they are not being addressed, it is because they lack the experience in knowing how to solves such issues.  If a person has done this test and the sound system provider or acoustical expert is not addressing these issue, they are not qualified for correcting sound problems in a church.  It’s like asking a Doctor who specializes in kidney problems to do Brain Surgery. What is needed a Brain Surgeon who knows how to fix both the acoustics and to design a proper sound system.

Get the church correctly evaluated before investing in that next sound system.  It can save those responsible a lot of disappointments down the road.  Fixing a room can cost less than replacing a sound system, or it could mean reducing the size of the suggested new sound system.

* Doubling the power required calibrated volume controls or switches to set up correctly as a viable test.

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New Church Sound System Equalization Schedule

Posted by jdbsound on February 17, 2016

Notice to all Clients of JdB Sound Acoustics.

If you are in a new church building or you have done major renovations in your church, you will have to re-equalize the sound system many times in the first few years.  Here is the Schedule you should follow.

  1. First year – After the 1st month, 3rd month, 6th month, 9th month and 12th month
  2. Second year – After the 4th month, 8th month and 12th month.
  3. Third year – same as year 2
  4. Fourth year – after the 6th and 12 month.
  5. Fifth year – same as year 4
  6. Sixth to tenth year, every 8 month.
  7. After that, once a year.

It take up to ten years for most building to fully cure or longer depending on how much concrete and wood is used.  For that reason, the humidity of the church becomes lower and lower as the church ages which also changes the sound of the worship space.

Also, depending on the climate area you are in, you should be re-equalizing your church sound system for each season.  more so the further you are from the equator.  If you have a digital processor or mixer, you can have presets for the room changes.

Joseph De Buglio

 

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What is the difference between scattering sound and diffusion of sound? Are Diffusers Programmable?

Posted by jdbsound on April 26, 2015

The simple answer is as follows.  Half, quart or third round devices or objects individually just scatter sound.  A single barrel diffuser or tube radiator as I often call them just create a very uneven distribution of sound.  As single units, it gives about the same amount of performance as placing a flat object of the same size and placing at a 15 to 35 degree angle on a wall.

When using barrel diffusers in various sizes and/or in spacing varying from 0 to 30 inches and apply them to all of the walls in a confined space, you are creating a diffusive field.  You’re turning the church walls into a phase coherent sound field – like churches of yester year built between the 1400’s to 1700’s.  When barrel tubes are used as a system you can program them to only manage the acoustical problems you want to get rid of and at the same time create a more desirable sound field like real reverberation that is musical and supportive to congregational singing.

Barrel tubes spaced too far apart just scatter the sound and reduces some bass but does nothing much else.  Instead, you can program the diffusers to manage standing waves, bass buildup, notch a frequency or two and equalize a room.  You can also program them to lower stage noise, manage monitor spill into the audience and improve congregational singing.  They can also be programs to make the sound system perform better.

The software to program barrel diffusers is still in development.  In the meantime, a test room, and a data base of real world testing is the best way to predict the final outcomes.  Try and program a digital EQ to cut 350 hertz 40dB.  It can be done but it sounds awful.  When you program tube radiators to cut 40dB, it sounds sweet.

Joseph De Buglio

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I Hate Mute Switches!

Posted by jdbsound on April 19, 2015

At my church, we still have an analog Mixer.  It has 24 channels, 4 sub groups, Left/Right and Mono out.   We use the sub groups.  Vocal, Drums, Instruments and Leadership mics.  The mixer has mutes on every channel, on each of the mute groups and on the 3 master outputs.  Fortunately, we have a church were the acoustics are stable.  We can run all of the mics open without feedback for normal worship levels. Monitors are stable and so on.  It is also a good sound rig.  When I run the mixer, I turn every channel on and shut off any mute switches.  I control all of the levels with the sub groups.  I don’t want any surprises.

This Sunday it was my turn to run the mixer as we are on a weekly rotation.  Thursday night was rehearsals.  Missed the rehearsal.  Friday night the Youth used the sanctuary and someone used the mixer.  Things were changed but it only took about a minute to set everything back.

As usually, you arrive at the church early for a pre service warmup. Dialed up a great monitor mix.  Everything seem right and as typical, we rehearse and warm up with the FOH speakers off.  When the worship team stopped it was time to turn on some background music.  Turned on the CD player, saw activity on the channel, raiser the fader for the channel and the channel was assigned to the Mono Main Out.  Raise the mono out and nothing happened.  What!!!

Checked the power switch to the powered speakers.  Check to make sure the processor was on and passing a signal.  Nothing.  Called the head tech for the church, he checked everything out. He checked the mixer and he agreed with me and thought that the power switch was faulty.  He removed the power switch and bypassed it.  Still no sound!  Double checked and found that the power lights on the back of the powered speakers were indeed on.  The head tech and I stared at each other confused wondering why there was still no sound.  Then he looked at the mixer again and this time noticed that the Mute switch on the Master Mono Main out was engaged.  He hit the mute switch and the rest of the sound system came to life.

In the year of mixing at the church, the Main Left/Right and Mono outs have never been muted.  The mixer is a spilt mixer where 16 channel are on one side of the mixer, 8 channel on the other side of the mixer and the Groups and master outs are near the middle of the mixer.  For some reason we were blinded in not seeing the red mute lights in that area of the mixer as there are other red lights in the area for other things.

Later I learned that a recently hired youth leader came from a church were the sound system was so unstable that you had to mute everything all the time.  They muted anything that wasn’t needed and because they left the mixer on 24/7, they had the habit of muting the master outputs as well.  The head sound tech and I had a good laugh at the whole experience.  For me, I should have known better as this is about the 3rd time something like this has happened.  This is the first time with powered speakers, but before I had people thinking there was something wrong with the mixer.  So please, unless you have a wonky unstable system, please don’t use the master mute switches.  They are great for a studio but not for live sound.

Joseph De Buglio

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Question! What would you do to fix the Acoustics of this Church?

Posted by jdbsound on April 1, 2015

You have a church that seats 750 people.  It is a simple rectangle room with 30 ft walls, 40 ft to the peak, 80 ft wide and 140 ft long.  The reverb is 2.2 seconds at 300 hertz and 1.3 seconds at 2000 hertz.  An Energy Time Curve test show reflections over 30dB at one second on the ETC in the 300 hertz range.  The floors are carpeted and the pews are padded seats and backs.  All of the walls and ceiling are insulated drywall on 12 inch centers.  Basically there is about 30dB of excess energy at 300 hertz.  300 Hertz has a wave length of 3.75 ft. The church has already tried 4 different sound systems over 10 years and all of them were designed and installed by companies that are supposed to be the best in the business and they all started off saying that the room needs to be fixed – but church board members vetoed anything that would change the aesthetics of the room – but it was OK to hang 2 ugly line arrays which lasted only 6 months.

The church is now asking for another sound system but this time all of the professional audio companies turned down the project and said to the church don’t call us back until you fix the room.  Now the church board has relented and they are allowing acoustical panels to be mounted on the walls. What acoustical method or system would you use to fix the problem?  What will reduce energy 30dB in this space?

For all the walls in the church, between windows, doors and bulkheads, there is only 35% of the total wall space available to mount acoustical panels on. Major issues are – Stage noise, floor monitors as loud as main speaker system in the first 10 rows.  Only 20% of the congregation is ever singing. Speech intelligibility is below 85% in full range – if you roll off the sound system at 200 hertz speech intelligibility improves to 88%.  Gain before feedback is very poor after 3 or more microphones are turned on at the same time. Subs never really sound right.  Pastor hears echoes all the time off the side walls when preaching. Drummer can never hear himself or the other worship team members – even with the headset monitors. The are currently using electronic drums but they have tried drum shields and booths without much satisfaction.

The church used to have a 40 voice choir but they never sounded very good and now with over $150,000 invested in a praise and worship team with all the latest state of the art technology and higher trained sound engineers, they sound no better than what the choir did years ago – but they are better at entertaining people!

(note: this is a fictional church but this is based on actual events that have happened recently in three southern Ontario Churches.)

Joseph De Buglio

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New Article on Sound Loudness in church

Posted by jdbsound on January 20, 2015

Just another article on the ever increasing sound levels in church.  Is it good or bad for the church community?  When a congregation can singing at 105dB, are they damaging their hearing even though they are singing acapella?  Click here and find out! 

Article written by Joseph De Buglio

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All Sound Systems are like magnifying glasses of the room acoustics

Posted by jdbsound on December 10, 2012

Is your sound system making the right impression?  Are the acoustics of your church allowing your sound system to make that great first, second and third impression at your church?

Once again the subject of getting more performance out of the next sound system upgrade keeps coming up. When a church is constantly seeking to get more performance out of a sound system at every upgrade and not be  enjoying the best sound possible then it’s time to fix the room instead of putting it off and investing into more equipment. This is the message your sound system is broadcasting.  Are you listening or are you waiting for the next technology breakthrough for that sliver of improvement?

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Calvary Worship Centre, Surrey, BC. Canada

Posted by jdbsound on November 9, 2012

Image

The acoustical system at Calvary Worship Centre is now about 95% complete.  The church hired me back to confirm the acoustical results and to finalize the sound system setup.  The Midas Pro2c Mixer and Danley Speaker system are a great match.

This is not the largest church to use this acoustical and sound system combination, but it is the largest church to change their acoustics in less than 30 days.  The fastest church repair was done in 7 days in Brentwood, England.  The largest Church I have worked on was 6500 seating.

A member of Living Hope Church in Surrey BC where they have been using the same acoustical system for over a year commented with saying Calvary has the same balance of sound as does Living Hope which is a modest 270 seat church.  Calvary Worship Centre can seat up to 2000.  That is remarkable considering that one place is built as a “proper” church and the other is a converted warehouse and both spaces perform the same.  (I was reminded that Living Hope Church thought they already had good acoustics but tried the Solomon system as a short term experiment.  The experiment turned it a permanent installation and the congregational singing and worship has never been more exciting.)

A Member of Calvary Worship Centre said, “The sound is far better than I dared hope for this 20,000 sq ft space given my previous church experience in a very similar venue.  Also, the total price was less than I expected it might be including your fees and the acoustic treatment.”

As one person mentioned at another church fixed with half round diffusers in Little Rock, Arkansas USA, he said, “you can tell if you have a good room by the number of people singing.  Before only about 20% of the audience was singing most of the time and for familiar hymns about 25% were singing.  Now it’s about 85% of the audience is singing all the time and you can hear the excitement and power of all those voices ring out.”  Imagine that – worship and excitement in the same sentence.

Click on the Photo to see the full size version.

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The question of…

Posted by jdbsound on August 20, 2012

The question of the day is, What was the purpose of the Palm Trees in Solomon’s Temple?  Was it practical, spiritual or something else?

Perhaps If I rephrase the question.  Were the carvings of the palms trees in the holy of holies added for symbolism or where they added to solve a problem related to hearing inside the two main rooms of the temple?

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