Humming Noise

[namsag]

It will be the devilishly fiendish chinese tunnelling from the other side of the world ready for the invasion of western europe and then world domination ,mark my words .
And when it happens reidy you can say i heard them first but no one would listen to me.

 

[Agile]

They just said that my hearing was fine and normal never said what the frequency range was.

Just spoken to EHO they say that they can do no more as this is not a nuisance matter - any suggestions of anyone who may be able to deal with this for us?

Thats an interesting statement! Its clearly causing you a nuisance ! But as he cannot hear it himself then its perhaps unstandable.

Did you turn off the gas at the emergency control before the meter following what I had said?

Also be aware that the electricity meter is still powered even when the CU is switched off and the older disc meters have a constantly powered energising coil which do hum. The supply fuse would have to be removed to depower it. They should be sealed though but in your situation you might choose to break the seal in your frustration to resolve the source.

Tony

 

[John506]

Don't know if anyone has already said this but can't be bothered reading through all the posts.

Have you got a cold water storage cistern in the loft? If you have go up there and see if the noise is coming from inside that.

 

[Softus]

 

[picbits]

You need someone to hook up an 'scope with a sensitive microphone (try and grab an old Tandy PZM one off Ebay - they aint cheap though).

Hook the scope up to the microphone, make sure everyone is quiet and look for the frequency of the hum.

If its 25hz, 50hz or 100hz then its likely mains induced hum.

Let me tell you a little story.

When I worked as a Technical Center Manager for one of the large PC stores (have a guess !!) we had a customer who kept bringing back monitors as they flickered. We tested them in store and there was no problem. The moment the customer plugged one back in, the picture would start shimmering and flickering with the colour focus going out.

Turned out he had a lot of electrical wiring in the wall behind where he was using the monitor along with metal pipes and this was causing the problems.

Any nearby pylons / underground electrical cables on or near your property ? Metal used in house fabrication can pick up EMI from these and hum at the frequencies I've pointed out above. If the metal is in your foundations/walls (even copper pipes can resonate under certain conditions).

I wish I lived closer to you - it would be an interesting little diversion to designing automotive equipment trying to work out where the noise is coming from.

I have a hum in a couple of places in the house. One is the airing cupboard where the old motorised timer is mounted on a plasterboard wall. The wall amplifies the humming. The other is in the kids bathroom where I can hear the transformer for the shaver socket. Took me a while to work that one out as its mounted in a blockwork wall and it transmits the humming through the front wall of the house.

As said above - sensitive microphone (PZM as it captures sound from all directions) and 'scope and try it in every room to work out where the sound is loudest. By comparing room sound levels you might be a bit closer to finding out the source.

 

[PlanetThanet]

Hi

Maybe you could form a support group,here's a start...... http://forums.moneysavingexpert.com/showthread.html?t=1085439

Or contact Torchwood?


Thanet.

 

[Agile]

Hook the scope up to the microphone, make sure everyone is quiet and look for the frequency of the hum.

The wall amplifies the humming.

I doubt that the OP owns a scope! When some of us mentioned that a hand held scope was a very valuable tool for boiler repairs, most poo pooed the idea but it turned out that several of us use them to advantage.

What advantage do you think that would have over a simple audio level meter? The EHO brought one I think but was unable to find any noise source.

I have to disagree with you about a "wall" doing any amplification!

A wall is a passive object! I agree that it will act as a sounding boads and make the sound easier to hear but unless additional power is added then it cannot be classed as an amplifier.

Also I dont see how a 25 Hz frequency would ever be produced in the home from a 50 Hz supply.

Tony

 

[picbits]

Hook the scope up to the microphone, make sure everyone is quiet and look for the frequency of the hum.

The wall amplifies the humming.

I doubt that the OP owns a scope! When some of us mentioned that a hand held scope was a very valuable tool for boiler repairs, most poo pooed the idea but it turned out that several of us use them to advantage.

What advantage do you think that would have over a simple audio level meter? The EHO brought one I think but was unable to find any noise source.

I have to disagree with you about a "wall" doing any amplification!

A wall is a passive object! I agree that it will act as a sounding boads and make the sound easier to hear but unless additional power is added then it cannot be classed as an amplifier.

Also I dont see how a 25 Hz frequency would ever be produced in the home from a 50 Hz supply.

Tony

Hmm where do I start

If you have a piezoelectric element, it will produce very little noise until its placed on a surface to resonate the sound (or in a tuned enclosure). Put my CH timer on a solid surface and it will stop humming. Press against the unit and it will stop humming. Place it on a badly built plasterboard wall and it will hum like crazy (good old new build houses). The wall has a certain amount of flex in it which moves with the CH timer making it into effectively a large speaker. Some nasty car "woofers" bolt to the chassis using it as you say a sounding board or turning it into a speaker. If you run it not bolted down, it makes very little noise. If you bolt it to a Citroen it will make a lot of noise. If you bolt it to a car with a "proper" chassis it will make less noise.

An audio level meter will tell you that there is a noise. It will not tell you the frequency of the noise. Sometimes finding the frequency of the noise leads to finding where the noise originates. If the frequency of the noise is say 83 Hertz then its unlikely to be caused by mains hum. This can rule a lot of theories out.

25Hz audio (if I remember rightly) can be heard sometimes on half wave rectified devices. 100Hz can be heard on full wave rectified devices.

Its just a thought - if the OP has a friend with a scope and a microphone its a very easy test to make to see if there is any constant hum. A sound level meter might pick up constant background noise which has nothing to do with the hum but visually on a scope, patterns can be visually recognised.

I use a few scopes in my work - I've got a cheap (<£100) handheld scope for general bench/mobile work and some equipment that cost more than I dare to think about for the more accurate measuring and datalogging side of my business.

 

[picbits]

And if you want to be really picky (which I know you hate being Tony ) you could use a spectrum analyser instead of a scope but these are a fair bit rarer (and more expensive) than a scope.

If the hum is not a factor of 50Hz it should still not be rules out as electrical as some motors will run at a multiple of 50 (RPM) but slippage on inductor motors means the motors can run slower than their theoretical nominal speed (there is a formula to work it out but its been a long time since I was last at college).

Anyway - I'm rambling now so back to you

 

[Agile]

25Hz audio (if I remember rightly) can be heard sometimes on half wave rectified devices. 100Hz can be heard on full wave rectified devices.

Unfortunately you dont remember correctly!

A single pulse from a half wave rectified 50 Hz supply will still be at a frequency of 50 Hz !

To pruduce 25 Hz from a 50 Hz supply is much more complicated although it was used during the 1940s and 50s in the mains operated telephone ring tone generators.

Tony

 

[picbits]

Unfortunately you dont remember correctly!

More than likely down to the effects of Guiness (and babysitting) while the wife is out with her friends

25hz is right at the lower limit of the average persons hearing anyway so its unlikely to be that low a frequency.

 

[tryitandsee]

Hurry up and find this noise soon Reidy, this thread is starting to get complicated

 

[RigidRaider]

Picbits you know enough about this to make a career out of analysing people's wierd noises!

What part of the motor industry are you in? My brother is with IAV (consultancy) in Detroit, trying to convince the Yanks they need small diesels.

 

[picbits]

My wife works in the motor leasing industry.

I run my own small business desigining electronic stuff for the "boy racers" and motor enthusiasts.

I design, build and sell custom designed gauges (electronic - think Knight Rider), rev shift lights, speedometer/odometers, converters to allow different types of dashboards to be fitted to different types of cars, datalogging devices - you get the general idea.

I've had years of developments, some of the projects are out there on the market, some went out for beta testing and ended up being redesigned a number of times before I was happy with them, many are still in the development/testing phase. None are making any big money yet but we're getting there

I might not be making much money but the bottom line is that I'm doing something I enjoy and it fits around having to look after a 10 year old with a disability.

 

[Agile]

Do you know how I can change the battery in the plip on my Peugeot 406?

And how it interfaces with the security keypad? ( Thats when it has a battery! )

Tony