Why?

70 dB is not much and 40 dB is practically church mouse quiet.....

We typically specify 85 dBa as the max for machinery.

Actually the dB value i given was not exactly same. Im doing some business with drilling stones. but their is the complain from naighbours that when i using drilling machine its very noisy. Actually the sound abit loud.

hasantha84

Short of insulating your walls to confine sound, until they make rubber drill bits your kind of stuck to sound insulating barriers.

You could buy them sound cancelling headphones for the holidays!

It is very likely low frequency ground transmission. Hard to mitigate.

Try keep pouring water at the point of drilling.It may reduce sound to some extent.

Look at one the Bose active sound suppression systems. They sample the sound, invert it, then play it back to cancel the original sound. I have seen these used in airplane cabins to suppress engine noise, so they may work in LF ground conduction.

google acoustic buffering when accessing vaults

Sound cancelling amplifiers are available. It works like this. It picks up sound waves from the equipment and plays it in the reverse wavelength through speakers placed near the noise creating equipment. Thus the sound and vibration both get nullified. I would ask more people to find out about it and notify our client.

One sound can't be nullified by another sound with reverse wave length. There is no such thing as reverse wave length. If it is possible to nullify by playing opposite sound, we can install it in jet engines,rocket launching sites and many many factories. You can switch on this gadget while taking to your boss.

Though it is possible he has a point and it isn't that simple either within the scope of the OP's question though it is possible.

See http://en.wikipedia.org/wiki/Noise-cancelling_headphones

By reverse wavelenght he meant opposite polarity (shifted 180 Deg.). Maybe not the correct words, but I think everybody understood.

And yes, it is posible to nullify a sound by playing opposite sound.

Also aircraft is the first application I heard of for such devices.

20 years ago I was dreaming on inventing such a thing, but I dropped it when I read that it already existed.

Yahlasit

Actually, not quite correct, 180. Deg out of phase would only give us a reversed echo of the main sound.

It's got to be in phase with it, but inverted.

Sorry

Yahlasit

In noise reduction attempts end user can device his own facilities.

In your case you can arrest the dissipation of drilling noise by means of providing a flexible rubber bellows with ring bottomed rubber flange so that the noise can be arrested. The bellows can be transparent so that working can be seen from outside.

You got to open the bellows, position the drill tip, close the bellows with bottom rubber ring and start work.

Upward drills the covering got to be sealed by suitable means.

Try this on a small scale driller and proceed.

The bellows and ring bottom should mainly cover the drill bit.

The problem with active noise cancelling systems, or anti-noise, is that they only work with airborne sound. The main mode will probably be sound conducted in the ground. In principle it might be possible to build an anti-noise system with ground mounted transducers, but I am not aware of any and they would be hideously expensive. Some tools are noisier than others, older jack-hammers have very noisy exhausts and these can be muffled as can the drill body. However this will not address the main problem of sound conducted through the ground.

I worked for a startup for 5 years that was in direct competition with Bose, David Clark and others developing active noise and vibration equipment including headsets AND transducers for vibration control. We had the counter rotating balance shaft removed from a v-6 Ford engine and used active motor mounts to reduce the cabin noise by as much as 20 dB at some frequencies. Transducers for this application would be about $100,000.00 USD each.

We had Harman Industries build a couple of transducers(loudspeakers) to quiet the M-1 tank diesel exhaust. They were very pricey, but you couldn't hear the exhaust from the tank. Track noise, being random was more difficult to cancel. The noise must be periodic to properly cancel.

Steve S is correct. This sounds like vibration induced noise. There is no way that you can get to 40dB and do any work.

I doubt the numbers you quote are correct.

If the sound transmission is airborne, then a simple wall or a line of trees around your operation will help significantly.

If the sound transmission path is through the ground it becomes a bit more complicated, and it really depends on the transmission path and the local geology.

Sound cancellation equipment probably will not work in this case as the noise is likely impulsive which would be difficult to cancel.

If the source of noise generation is through some electrical device, then noise cancellation filters or nullifiers could be applied to reduce the same. But if the noise source is mechanical, like drilling, will these devices work?. As far as I know sound already produced as vibrations, has some energy which can not be annihilated or reduced to zero. We can reduce the noise by means of reducing the vibration at the source by using some dampers ,by lining the reflecting surfaces near by with sound absorbing material and also by isolating the sound generating part . Each of these can be achieved by using several techniques. If I am wrong please correct me and enlighten me on the anti sound wave producing or silencing devices.

Cutting a channel in the soil or rock between the drill and the offended party would produce a substantial reduction of sound transference.

I agree.

And how do we silence the digging of the channel? - with an even bigger one around that?!

Proper prior planning prevents piss poor performance

Get a permit, cut the channel pour in expanding foam or wear soft shoes.