Soundproof My Generator

 

Nobody wants a noisy generator that disturbs the family and annoys the neighbours - we get it. Or perhaps you're a business owner and need to avoid drowning out the telephone conversations in your office, patrons in your restaurant  or falling foul of noise regulations in your housing or office complex? 

 

Generators offer the convenience of being powered up when Eskom power is down but if the problematic noise generators create is not dealt with - they are a nuisance.

 

Genesis Acoustics provide expert advice and commercial grade soundproofing solutions that have a proven track record. Our results speak for themselves, read on to see the testimonials below and watch the demo videos on the product pages that follow.

 

 

 

Real Solutions

Backed by Real People 

 With Real Acoustic Experience

What you won't get from us:

A DIY hack based on urban legends like convoluted bedding foam, egg boxes & polystyrene - we've seen these mistakes and more, over many years as working professionals in the soundproofing industry. Our approach is to do it properly or not at all. At any rate, there's no such thing as a cheap fix - just wasted money on solutions that don't work, are a fire hazard and likely to cause your generator to overheat. In South Africa we have a great saying "Goedkoop is duurkoop" in other words, it may seem cheap now but it's going to cost you more in the long run, in terms of wasted money, time, energy & lots of frustration - no one wants that.

 

What you can expect:

✪ Friendly, professional advice. 

✪ Free advice over the phone or e-mail. You're also welcome to make an appointment to come in see us at our premises for a no cost, no obligation chat.

✪ Paid site inspections. This is the fastest way to get you a quote, for a solution designed to meet your exact requirements. Enquiry forms are on the relevant pages of our website.

 

A choice of:

✪ Complete prefabricated soundproof enclosures in 3 standard sizes

✪ Custom made soundproof enclosures

✪ Outdoor, all weather LF125 noise barrier panels in a range of standard sizes

✪ Supply of all the separate soundproofing components 

✪ Supply and installation by our trained staff. Check with us to see if we install in your area.

Can't I just buy a silent generator?

 

I hate to be the one to break it to you ... but so called silent generators aren't actually silent. I know you'd think so - right? Even this cat can't believe it. 

 

In fact, we get clients coming to us all the time who own silent generators and still require soundproofing. We've found that so called "silent generators" generally operate at about 74-76dB which is still loud enough to disturb the peace, especially when the generator has to run for 2-4 hours during load shedding and in the quieter night time hours the noise is even worse.

 

Q. Ok, so soundproofing my generator is necessary for mental wellbeing  😄  but how much does it really help? 

A. I'm glad you asked, here are a couple of short testimonials from our clients.

 

 

⤞   Testimonials   ⤝

 

Here's what some of our clients have had to say ...

 

Mr Nairin - Home Owner 

Midrand, JHB, RSA

 

“A very good job was done, the enclosure indeed lowered the noise levels. We are very happy with the results. Before the soundproofing, the generator noise measured 97.8dBA but after the soundproof enclosure was installed, the sound level dropped to 59.2dBA at 1m from the enclosure. Well done”.

 

 

 

Mr Landman - Home Owner in Boskruin, JHB, South Africa

 

“This enclosure worked wonders! Completely sorted out my problem with the neighbours and allowed us to sleep or watch TV while running the generator as well. I couldn't believe the drop in sound that was achieved, it was mind blowing! We were not even aware the generator was working at times. Thank you Genesis Acoustics for a job well done and the peace of mind.”

 

Mr Jaffer - Home Owner

Duinfern, JHB, RSA

 

“Even though I was away on business during the installation, I was amazed when I got back, seeing a well constructed generator enclosure. The enclosure helped reduce the noise made by my big generator to a level that my neighbours cannot complain about it anymore. I am happy with the results."

 

 

My goal on this page is to equip & inform you

I can help you avoid all the common pitfalls - of which there are many.

The next page will be about identifying your needs 

and directing you to the best possible solution but first 

I'd like to equip you with some important info.

 

Let's define noise levels

Noise is measured in decibels, so it's important to gain 

a basic understanding of how the decibel system works.

I'd also like to make it relatable for you with real world examples.

Decibels

Understanding the Scale

 

A decibel, or its abbreviation dB, is a measurement of loudness

Decibels operate on a logarithmic scale & go up in powers of 10

Different weightings are applied to the decibel but the weighting used to measure noise, as regulated by municipal by-laws, is the A weighting, which  is written 

as dBA.

A 1dB difference is not perceptible to the human ear

A 3dB difference is just perceptible

A 6dB difference sounds much softer / louder

A 10dB decrease will sound half as loud

A 10dB increase will sound twice as loud

So a sound of 20dB is 10 times more intense than a sound of 10dB and a 30dB sound is 100 times more intense

Sound levels are measured on a sound pressure level (SPL) meter. The meter must be calibrated to provide an accurate reading. A calibration certificate must be provided.

SPL Meters come as a class 1 (required for all legal work) and a class 2 (for all general purpose readings).

Real Life Examples & Effects

 of Common Sounds in Decibels

 

30dB Quiet bedroom at night

40dB Quiet library

50-70dB Normal conversation, quiet office

70dB Intrusive, interferes with normal conversation

80dB Annoying. Constant exposure may cause damage

70-85dB Vacuum cleaner, hair dryer, dishwasher, city traffic

85db Eight-hour exposure can cause hearing damage

85-99dB Generator, lawnmower, motorcycle, food blender

90-100dB No more than 15 minutes unprotected exposure recommended - to avoid hearing damage

100dB+ Regular exposure for more than 1 minute risks permanent hearing loss

100-120dB Chainsaw, jackhammer, dance floor, boom box, rock concerts

This may sound weird but ... 

> What does generator noise look like?

> And why is this important to understand?

It's important because once you visualise the sound signature of a typical generator then you can appreciate what it's going to take to actually solve the noise problem. 

 

To make this easy for you, I ran an RTA (real time analysis) of generator noise to illustrate this point. The measurement was taken during load shedding, in the open air, the generator was mounted on a trailer with no enclosure and the reading was taken at a distance of 1m. 

 

Note the sound pressure levels in the low frequency (LF) range. There is a very evident peak from 57Hz to 125Hz, with significantly high SPL through to 2000Hz and only a slight drop off after that. 

 

This shows us that to effectively deal with generator noise, products are needed that are especially efficient at dampening low frequency (LF) noise.

 

In fact, the majority of noise complaints arise because of LF. Why? Because the wave length is much greater, LF noise travels much further than sound in the mid to high frequency range. This is why, when there is a loud party a few houses away, you normally can’t tell what song is playing but you can clearly hear the bass i.e. LF noise. The same applies when a taxi drives past.

 

Therefore, an acoustic treatment that fails to adequately address the LF noise problem fails altogether. No all sound absorption is equal, convoluted bedding foam for example has terrible sound absorption in the LF range yet we regularly find it pasted inside generator enclosures. It goes without saying that these same still people come to us for help to solve their noise problem.

 

This is what proper sound absorption data looks like

 

Noise reduction coefficient (NRC)

The arithmetic average, to the nearest multiple of 0.05 of the sound absorption coefficients 

in the 1/3 octave bands centred at 250Hz, 500Hz, 1000Hz and 2000Hz.

 

Understanding a Sound Absorption Coefficient - in Layman's Terms

It's a percentage sound absorption therefore

0.69 = 69% sound absorption at that specific frequency.

0 = 100% Reflection (although in practise some sound energy is always lost)

1.0 = 100% Sound absorption

 

Here's the most important take away:

The level of sound absorption must always be appropriate to the sound signature of the noise.

i.e. For example it's useless to have  a high absorption coefficient of 0.9 @ 2000Hz when your main noise problem is @ 125Hz.

Sound absorption is not even at all frequencies, this is due to the differing wave lengths/amplitude of sound, at different frequencies.

9 Mistakes to Avoid 

When Soundproofing Generators

 

Going through this list will save you a lot of wasted time, effort and money.

 

These comments relate specifically to the topic at hand. I'm not knocking

any product, I'm saying use the right product for the right application.

1. Polystyrene

I can't understand how or even why this urban legend started but nonetheless, it's commonly believed that polystyrene has good sound insulation properties - in fact nothing could be further from the truth. Polystyrene is a simply terrible insulator of sound. It takes mass to attenuate sound and polystyrene is a very lightweight product. 

 

I have had many people over the years who have installed polystyrene ceilings and then battle with privacy between adjacent rooms, as sound passes over the walls and straight through the ceiling with very little resistance. I hope this is not a problem you can relate to but if it is we can help.

 

Please stay away from polystyrene for soundproofing purposes.

 

2. Egg boxes

This urban legend persists despite any proof to back it up. I still get people asking me if egg boxes will work and sometimes they've been diligently stock piling them for weeks. I think people just desperately want to believe that something that costs them nothing will actually solve all their acoustic problems. 

 

The uneven profile with the peaks & valleys are what give people hope that this will somehow break up the sound energy or diffuse the sound waves. However I've seen actual acoustic data that shows that the sound absorption offered by egg boxes is terrible and they don't offer any kind of useful diffusion either. A proper diffuser has to be acoustically engineered to work at specific frequency bands and they are typically only used in critical listening spaces such as recording studios, hi-fi and high end home cinema rooms. Even a proper diffuser is not used to stop sound but to enhance the quality of the sound in a room.

 

There is a good reason chicken farmers don’t make a good living on the side doing acoustic treatment. Forget this one and move on.

 

3. Open cell polyurethane foams

Don't use open cell polyurethane foams as they:

> Do not have sufficient density to attenuate noise

> Lack the necessary sound absorption properties in the important LF range

> Are highly flammable and emit toxic gases if they burn. Yes, I know firsthand of people this has happened to. While there are flame retardant polyurethane foams, they will still burn, they will just burn at a slower rate and they will still release the toxic gases as they burn.

 

There is a reason bedding shops aren’t acoustic experts - not all foams are created equal. 

Use that sheet of convoluted bedding foam as a mattress topper on your bed - where it belongs.

It is not designed for use inside a generator enclosure.

 

There are of course genuine acoustic foams which are developed for that express purpose and should always come with certification, from an independent lab to prove it's credentials. Acoustic foams are typically used in recording studios and band practise rooms and are well suited to these applications.

 

4. Hardware store thermal insulation 

Hardware store grade, thermal insulation products are not specifically designed for soundproofing, they're designed to lay flat horizontally and provide thermal insulation over a ceiling. The density of these products is far, far too low for any meaningful soundproofing, at the sound pressure levels produced by a generator. We get people who come to us on a weekly basis who have tried to use these products for soundproofing and been disappointed. Also when they are used in vertical applications they sag and leave empty hollows which allows sound transfer.

 

I'm certainly not against thermal insulation, just use it for the intended application, to keep your home cool in summer and warm in winter.

 

5. Closed cell foams

Don't use closed cell foams for lining the inside of the generator enclosure for sound absorption or as a sound barrier. They do not absorb noise efficiently and there are better products to provide sound isolation from airborne sound. 

 

A suitable application for this type of product, is as a seal to close air gaps or to isolate certain types of vibration - in these specific applications the product works well.

 

 

6. Timber board

It's tempting to use boards such as shutterply, OSB or chipboard to fabricate a generator enclosure because these products are cheap and readily available but there are some serious drawbacks, they:

a) Lack mass. Ever heard of the privacy problems in timber homes? Eh, there's a reason.

b) Conduct resonance well - not a good thing in this context

c) Are flammable and it's just wise to put safety first, given that most home generators are stuck out of the way where they are not easily observed. No one believes that it will happen to them but it can and you don't want to be that person.

 

7. Big gaping holes for air flow

It should not surprise you that a large gaping hole will also allow noise to get out of a generator enclosure. However I've actually seen other companies in South Africa offering a simple timber box with big holes for airflow and calling them soundproof generator enclosures?! Man this makes me mad, I really don't want anyone to get duped. Yes, a generator requires airflow but large gaping holes are going to totally defeat the soundproofing objective.  Sticking a fan in the hole is also not going to be sufficient as it will not attenuate any sound.

 

 

8. Domestic grade extraction fans

To soundproof the generator it must be enclosed but as soon as you enclose it, you're going to have a massive build up of heat. If the enclosure isn't properly ventilated, the heat inside will continue to climb until eventually your generator dies, something catches fire or both.

 

That little plastic bathroom fan just isn't going to cut it. In fact I've yet to see any fan, in any hardware store that would work for generator enclosures and this is understandable as they are supplying domestic grade fans for the bathrooms & laundry areas in homes.

 

 

9. Air Vents

As stated above, a controlled airflow is necessary to regulate heat within the enclosure but as soon as you create a hole in the generator enclosure, you also create a weak point in the design where sound will escape. A simple vent is not going to be sufficient as it has no sound attenuation properties. A proper acoustic baffle is required to achieve both airflow and sound attenuation.

 

How loud is a typical generator?

 

Most generators in an open frame design operate at about 95 dBA, however there are generators which will be louder or softer than this.

 

How do I test how loud my generator is?

 

Ideally sound pressure level testing should always be done with a calibrated SPL meter, these  devices are typically very expensive but there is an alternative. To simply get a ballpark idea you can download a free Decibel Level Meter SPL app 

on your phone which will give you a rough idea how loud your generator is. Just realise the limitations, this cannot be used as legal proof. 

At best it's going to be within 3-4dB of what the actual noise level is. The noise level should be measured at a 1m distance from the generator. 

The app must be set to dBA.

 

The noise level of the generator can fluctuate depending whether or not it's carrying a load. In other words testing a generator while it is simply idling will not give a true indication of the noise level during load shedding.

 

It should be remembered that in terms of the law, the noise level would not be measured 

at your generator but at your boundary wall. 

The law & noise in a residential area

 

The following municipal bylaws may vary slightly depending on location so use the following as a guide.

 

Urban districts

Daytime: 55dBA

Night time: 45dBA

 

Some people naturally assume that complete silence is 0 dBA but in this context in an open air suburban setting, a very silent evening might be about 30dBA.

 

These noise thresholds may not be exceeded in the form of noise that is continuous.

For example: A friend hoots twice at your gate  

The noise is louder than the threshold but does not violate the law because it isn't continuous.

However a generator with no soundproofing that runs for 2 - 4 hours continuously would be in violation of the law regarding noise limits.

 

What happens if you're found to be in 

violation of the noise limits?

If a complaint is received and the municipality finds that you are exceeding  the noise limits they will issue you with an official cease notice and possibly a fine. You would then be prohibited by law, from using your generator until you could prove that you had taken measures to soundproof it and that it no longer exceeds the noise limits.

Well done, 

you made it to the bottom of the page!

 

Hooray 😃 🚀

 

You're better informed and a whole lot wiser.

 

Ok, now it's time to change gears and get into the specifics of:

 

✪ What you need

✪ Where you need it

✪ How it should be installed

 

 

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