Is Noise Pollution the Next Big Public-Health Crisis?

https://www.newyorker.com/magazine/2019/05/13/is-noise-pollution-the-next-big-public-health-crisis

Applying Green Glue Noiseproofing Compound

Noise management for venues

Usually, a noise limit is set, and if you go above it, penalties apply.

It is set at a fixed position in the venue and calibrated to a lower noise level at the receiving point (usually neighbour). For example, if anything over 105 dB LA_eq inside the venue causes excessive noise at a neighbouring receiver, the limit will be set at 105. It is usually measured at 3m from the PA system.

This is very common and suffers a multitude of problems...

1. Limiters are installed in the venue to prevent going over the noise limit. They either, turn the power to the PA system off when the limit is exceeded, or compress the music when the limit is exceeded.

• The power cut off system does give some warning but once it cuts off there is silence until it resets. There is a great story about a wedding for a very wealthy couple where the band was nicely under the limit, until someone started dancing wildly and the guests all started cheering and screaming. The limiter turned the sound off at that point and the rest is obvious....
• All sorts of illegal bypass methods are tried including covering the microphone and dangerous bypass wiring

• The compression style limiter does not turn the sound off but tries to turn it down as the music gets louder, and in doing so destroys the sound of the music.
• The most common problem with this type of limiter is DJs and sound engineers who either don't understand how they work or don't know they are installed. As they try to increase the sound level in the venue the limiter is “fighting” their efforts. They then try harder to increase the sound level so the limiter compresses the sound even more, until they give up in disgust and blame the PA system for sounding bad.

2. When a neighbour complains about noise from a venue it can be checked at the neighbour's property. The level is usually set at a small amount above background noise. Background noise is measured over a long period of time to average out spurious noises like vehicles passing. However, if there is more than one noise source at the time of complaint, things get difficult. For example, an area with bars and restaurants will have all of them contributing to the noise on a Friday or Saturday night. If a neighbour complains, it is really impossible to determine which one is responsible. Even if one is a little louder than normal, but still under it's own limit, the sum of all sources may be above the limit at the neighbour's property.
3. When setting noise limits, regulators use the sound energy equivalent to that of a constant sound pressure level for a set period of time – NOT the sound pressure level at any instant. This is to help the measurement align to the human hearing system and what it finds objectionable. The limit may be specified in units of La_eq dB or L₁₀ dB_. Venues using cheap sound level meters are not only relying on inaccurate equipment but they are measuring the wrong thing. Sound Pressure level (SPL) is not La_eq dB or L₁₀ dB, and the heated arguments starting with “but we had our sound level meter on all night and never went over the limit” are futile. It's a bit like having a 60km/h speed limit and saying “but I only went 30 metres”.

4. So what is the ideal situation?

• No power being switched off or compressed.
• Being able to prove that the venue complied with the La_eq dB or L₁₀ dB limit using a high quality system that securely logs all measurements for proof.
• Showing that the limit was not exceeded inside the venue and therefore complaints must be from other or cumulative noise.
• Ideally, a system that calculates the current La_eq dB and looks at the trend to give a “prediction” of if and when a limit may be exceeded in the future (remember, the limit is total energy equivalent to a constant level for a period of time, so it can be calculated on the fly). This allows a manager, DJ or engineer to simply turn it down a little.

The solution - the system of choice is called 10EaZy. It is a unique and intelligent design that succeeds because it considers the viewpoint of the regulator, venue, sound engineer/DJ and patron. 10EazY is even legislated for all venues in some countries.

Interestingly, feedback has shown that not only are limits managed better but sound engineers have have focussed more on creating a good mix than just turning it up!

For more information, acoustic advice or pricing, please contact us at;

info@ultrafonic.com.au

07 3103 0591

or go to the 10EaZy products page here.

www.ultrafonic.com.au

Common mistakes in DIY acoustics

Just goes to show that acoustics ain't that simple, when even someone like DPA gets it wrong. This is littered with errors caused by trying to precis a complex topic. 

By example, angling walls to avoid room modes is wrong. In fact it skews them and makes them harder to figure out. It doesn't make them any less.

But UNBELIEVABLY, they are quoting NC figures for background noise!!! This is derived from the human hearing response but microphones don't have ear canals..... So a decent NC figure can still have plenty of low frequency noise and guess what a sensitive mic does with that!!!


http://www.dpamicrophones.com/mic-university/10-important-facts-about-acoustics-for-microphone

NC Curve

Contact us on 07 3103 0591 or enquiries@ultrafonic.com.au

Church almost destroyed acoustically

I just did a design for a church as a paid consulting engagement. It is roughly 50 x 25 x 5m.

There is already carpet, upholstered seats, curtains etc. However there are some concrete, some SIP and some plasterboard walls. Obvious flutter echoes can be heard between them. 

The calculations show, with about one third occupancy, a reverberation time (RT60) of 1.6 seconds. For a room volume of about 6500m^3 this fine and agrees with AS/NZS. Rudimentary measurements confirm the calculation.

AS/NZS 2107:2000 recommends reverberation times of;
1.0 seconds for Spaces for speech
1.3 seconds for Cabaret and Theatre restaurants,
1.7 seconds for Music Studios;
for rooms of approximately 6500 cubic metres

With the room full it approaches 1 second, which is a little too low. Worship spaces are used for purposes that commonly require all of the above functions, so a compromise is always needed. Generally, a high RT60 increases the engagement of the congregation. More problematically, a low RT60 isolates people and they miss the community experience of the congregation. So the objective is to maintain a suitable RT60 and eliminate problematic echoes that may interfere with speech intelligibility or clarity.

They had originally asked suppliers of acoustic absorption to quote on what they needed. Of course this is like asking the Ford dealer what car is best - an obvious conflict of interest! A large polyester supplier quoted them almost 200 sheets of a mixture of 50 and 25mm thick polyester. This would have destroyed the acoustics of the room in terms of a worship space. But they would have sold over $30k in polyester! Not only that but the calculations on this amount show that after a certain point, adding more absorption makes very little difference i.e. the room is "killed off" with a small amount of absorption and the rest is just wasted.

I have advised them to add NO absorption and construct some simple diffusers to reduce the flutter echoes. This will maintain energy in the room for an inclusive community experience and reduce problematic echoes. If for some strange reason the result demands a lower RT60 some absorption could easily be placed on the ceiling - but I very much doubt it will be needed.

Including my fees, and constructing the diffusers, they have probably saved over $25k and avoided a complete disaster. 

So the message is, get qualified advice and don't ask someone selling a product how much you need....

Contact us on 07 3103 0591 or enquiries@ultrafonic.com.au

How to soundproof a wall that has no insulation in the cavity

Adding layers of plasterboard to a wall to increase the soundproofing may not yield great improvements if there is no insulation in the cavity.

It is reasonably easy to knock holes in the wall between the studs and above and below the noggins. Then you slide some insulation up and down into the slots just created.

Simple pink batts are sufficient. In this case we used some scraps of 32kg glasswool that were lying around to get rid of them. If you can, spread the insulation around in the cavity as it will perform slightly better than if it's all stuck in one corner. You can use a stick to push it around.

Then you simply put rough patches in the holes and plaster over them.

A bit of plaster cement and a quick sand and it's ready for a layer of plasterboard and Green Glue

Contact us on 07 3103 0591 or enquiries@ultrafonic.com.au

Soundproofing with Mass Loaded Vinyl versus Plasterboard

Here's an honest manufacturer - if you read their Mass Loaded Vinyl test data, you will see that it does the same as a similar mass of plasterboard. Of course plasterboard is cheaper and takes probably 1/10th of the time to install. Interestingly the say "Pay attention to the word INSTALL. Correct installation is critical to this product working the way it is designed to work." And if you have ever hung, taped and tried to seal MLV you will appreciate how almost impossible it is. Still, great to see honest raw data out there -

Read the article and test data here


Contact us on 07 3103 0591 or enquiries@ultrafonic.com.au