Noise Cancelation

[l008com]

So I started installing my stereo, but I haven't finished yet. The main unit is still not installed, but the two primary speakers are. Two 6.5's. So I'm driving around in my boat, not listening to tunes, instead listening to my loud outboard. After 3-4 hours of driving, you really start to get a headache. Half that headache is probably from 2-cycle exhaust but the other half is from the sounds, it's just so loud.

Then it hit me. Those two speakers are perfect for sound cancellation! Do they make any sound cancelation devices? All I'd need is a mic to mount up on the windshield. Then some small box that would power the speakers. Blam, no more engine sound. If the box was smart enough, it would filter out human vocal frequencies and not cancel those out, only engine sounds. I could stay in my boat all DAY if I could mute the engine!

But even if such a device exists and is affordable, there is one other question. How would I connect the stereo and this device to the same set of speakers. I can't use the stereo's AUX input because then there would be no music. This stereo (and very few stereos) can mix the different inputs. Although if it did mix the audio, the music would just get cancelled out too. So the 'black box' sound cancelation device would have to somehow take that into account too.

But I guess first thing's first. Do they make sound cancelation "modules"?

 

[Silvertip]

Re: Noise Cancelation

Only one problem with your idea. A mic on the windshield picks up sound -- whatever it is. That mic feeds an amplifier no different than the external amps used in high power audio systems. That amp then powers the speakers. So whatever the mic detects is what comes out the speakers. That would be more noise including the AMPLIFIED noise from your engine. Back to the drawing board. You can cancel the noise from the engine (and all other noise as well) by wearing a noise canceling headset -- or take the cheaper route and insert some foam ear plugs.

 

[l008com]

Re: Noise Cancelation

I disagree. A noise cancellation device would work just like they do in cars for example. They know what sounds they are making, and only 'cancel' out other sounds. It's a relatively simple audio filter to know what sounds you are making, subtract that, and then you see the raw sound you need to cancel. I'm sure someone makes things like this. If the electronics of this device were smart enough, it would filter out it's own sounds, filter out human vocal frequencies, and accept a pre-amp input from a stereo so it could also filter out that audio, so it also wouldn't get cancelled. In a setup like my small boat, where all the sounds come from the same direction, it should be pretty easy to cancel them out with offset phase audio.

 

[bruceb58]

Re: Noise Cancelation

Its done all the time. In fact there are electronic mufflers that have the equivalent of speakers and a microphone. Basically, they take the noise signal and create a cancelling signal which is basically a signal that is 180? out of phase with the noise signal picked up by the mic.

http://www.cdxetextbook.com/fuelSys/intakeExhaust/exComp/electronicmufflers.html

The same theory is done in noise cancelling headphones. The problem with a boat is that you would probably need a whole boat load of speakers to have a effect on what you hear.

 

[dingbat]

Re: Noise Cancelation

The best solution to canceling out the noise of a 2 stroke outboard is to buy a 4 stroke.

 

[l008com]

Re: Noise Cancelation

The best solution to canceling out the noise of a 2 stroke outboard is to buy a 4 stroke.

First person to buy me one get's a free boat ride! I'd love to have a direct-injected 4 stroke honestly. I'd probably get 2x the MPG or more. My little 6 gallon tank would last me all day and all night.

 

[Silvertip]

Re: Noise Cancelation

The best solution to canceling out the noise of a 2 stroke outboard is to buy a 4 stroke.

At wide open throttle there is very little difference in noise readings. The difference is in the "type of noise" rather than the noise level itself. Again, the Performance Bulletins page on the Yamaha web site is a good reference. It is very iinteresting however, that some of the more recent four stroke tests no longer list noise level. Hmmmmm.

 

[Silvertip]

Re: Noise Cancelation

First person to buy me one get's a free boat ride! I'd love to have a direct-injected 4 stroke honestly. I'd probably get 2x the MPG or more. My little 6 gallon tank would last me all day and all night.

No you won't get 2x the MPG unless your two stroke is so out of whack fuel is "running" through it without being burned. Do a search for "Fuel Economy Study" This topic has been discussed frequently.

 

[Silvertip]

Re: Noise Cancelation

I disagree. A noise cancellation device would work just like they do in cars for example. They know what sounds they are making, and only 'cancel' out other sounds. It's a relatively simple audio filter to know what sounds you are making, subtract that, and then you see the raw sound you need to cancel. I'm sure someone makes things like this. If the electronics of this device were smart enough, it would filter out it's own sounds, filter out human vocal frequencies, and accept a pre-amp input from a stereo so it could also filter out that audio, so it also wouldn't get cancelled. In a setup like my small boat, where all the sounds come from the same direction, it should be pretty easy to cancel them out with offset phase audio.

So you want to filter out noise -- noise that you can hear obviously because it annoys you. Human sounds, such as music (voice and instrumental) falls into the 20 Hz to upper teen Hz (20KHz to keep things in perspective). So if you can hear these obnoxious noises, they are in that frequency range. If you filter out or block audible noises and let others pass, what does that leave you with? My guess is music that has a bunch of holes in it. How obnoxious is that! If there was just one noise, and it didn't change in intensity or frequency (which your outboard does) I could see spending some bucks to cancel that noise. But the cost, size, weight, complexity and other factors to make your ride silent except for conversatiion and music would seem very impractical.

 

[seabob4]

Re: Noise Cancelation

I like the sound of a sweet running OB...

 

[zopperman]

Re: Noise Cancelation

how about some noise cancelling acoustical foam under the cowling...?