Hand-held "Sound Camera" Shows You the Source of Noises 114
Zothecula writes "If you work with machinery, engines or appliances of any type, then you've likely experienced the frustration of hearing a troublesome noise coming from somewhere, but not being able to pinpoint where. If only you could just grab a camera, and take a picture that showed you the noise's location. Well, soon you should be able to do so, as that's just what the SeeSV-S205 sound camera does."
Re:Screwdriver (Score:5, Informative)
Old but cool mechanic's trick: use a screwdriver. Place the metal against a running engine, put the ( plastic or wood ) handle against your ear. Hear amazing things inside of the running engine.
You can augment that by stuffing the end of the screwdriver into a length of rubber hose; you get the same effect, without having to stick your face 4 inches from the reciprocating assembly.
Re:Screwdriver (Score:5, Informative)
You can get a stethoscope with a metal probe at Harbor Freight (in the USA) for under $5. An amazing tool to listen to working machinery. Like the screwdriver, times 10.
Re:Screwdriver (Score:4, Informative)
I use that very one at work to find bad bearings and the like in vacuum pumps. One of the most useful $4 items I've bought.
Re:Open source sound localization (Score:4, Informative)
I'm wondering if you saw or read about a sound device that someone made a while ago, probably in the 1990s. A teenage girl won a science or engineering contest for building a device to help bird watchers find a particular bird they can hear, but not see through the leaves. It was a couple dozen tubes, like a big bunch of straws, cut to different lengths and mounted on a tripod.
When you hear the bird chirping, and can tell the general direction in the trees around you, you point this thing in that direction and move it around, and listen for the sound to get louder when it's pointing at the bird. It didn't use any microphone, or even a power source, just natural sound propagation in the tubes.
I've been googling for it for an hour now, but I don't even know what the device would be called. Do you know what I am talking about? Or at least what the device would be called? I guess it wasn't commercially made, or there would be a page somewhere selling them.
Bearings and gears, and shafts - oh my! (Score:5, Informative)
A ball inside a ball-bearing race typically fails by "spalling [google.com]": a tiny flake breaks off of the surface of the ball.
As it rolls around the race, the ball makes a periodic "tick" sound whose frequency is related to its rotation.
So... if you record the sound coming from an engine, and you have an index mark input (when the flywheel reaches TDC, for instance) and you know the gearing ratios of all the shafts, the inner race and outer race diameter of the ball bearing races, and the number of balls &c you can relate the frequency to a particular bearing which is going bad before it fails.
You can do the same thing for the races: the inner and outer races rotate with a particular speed relative to the balls, so a crack or spall on a race will also make a sound at a particular frequency.
Essentially, look for energy in the particular frequency that a particular failure in a particular bearing would make based on the engine RPM, and repeat for all races. If you find enough energy (ie - audio volume), you know which bearing is going bad and the nature of the problem.
A bad gear typically starts with a broken tooth: a crack forms at the base of the tooth, resulting in a tooth which doesn't push as hard against the mating tooth in the next gear. This causes the driving shaft to speed up slightly as the cracked tooth mates, and slow down for the next tooth due to inertia.
If you continuously monitor an accelerometer attached to one of the engine shafts you can see this speedup/slowdown signature, and if you know the gearing ratio you can figure out which gear is going bad within the engine. The crack tends to mature over time, so an individual tooth will first become "wobbly" before complete failure.
A Journal Bearing [efunda.com] typically wears when the "hole" becomes bigger than the shaft (the oil and mating shaft grind the hole bigger over time). When this happens, the mating shaft and attached mechanics will "wobble" within the hole, causing a noticeable shift in the mass of the engine.
If you continuously monitor an accelerometer attached to the engine block, you can index this wobble to the shaft speed based on the engine RPM and tell if any bearings are failing and how bad they are.
In all cases you can determine the nature and extent of the damage while it is relatively minor - before it damages other parts of the engine (scored shafts, pieces breaking off, catastrophic failure in flight, &c.)
At the time this was figured out the technology was expensive to implement, so it was only appropriate in select situations - aircraft maintenance, for instance.
Nowadays with the rise of high-power microprocessors and personal phone displays, perhaps some enterprising hobbyist will figure out a way to implement this for automobile maintenance.
Re:Open source sound localization (Score:4, Informative)