Shop noise

[Dave MacArthur]

I just went to buy some, but the Tiger link says they are no longer for sale? Does anyone have a good link to buy these logitech NC earphones Bob is raving about He convinced me.

[Carl Fox]

The type of electric motor in a device has a major effect on the frequency and intensity of the noise produced.

Ever notice that devices with small motors (vacuum cleaners, SCMS, hand-held belt sanders, hair dryers etc.) tend to be loud screamers, whereas stationary devices, (TS, jointers, Dust Collectors, etc) tend to have a low pitch (almost a pleasant sound, IMHO) and are not nearly as loud?

This has to do with the type of motor used in the application. Cheap, portable devices use Universal motors. These are light, cheap, small, and put out a lot of power for their size. They also are noisy like nobodies business.

The term 'Universal' is applied to a series connected motor; one in which the same current passes through both the armature (rotor) and field (stator). The power source can be either AC or DC, hence the name universal or series universal.

Expensive, stationary devices use Induction motors. Induction motors are expensive, large, heavy, and quiet.

An induction motor (IM) is a type of AC motor where power is supplied to the rotating device by induction. An electric motor converts electrical power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a DC motor this power is supplied to the armature directly from a DC source. But in an AC motor this power is induced in the rotating device. An induction motor can be called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. Induction motors are widely used, especially polyphase induction motors, which are frequently used in industrial drives.

To see what I mean look at your 2.5 HP router. The whole thing smaller and lighter than just the 2 HP motor on your table saw. Yet, when you turn them on the difference in sound pressure is dramatic.

Therefore the general rule of thumb is; if you can lift it, it probably has a Universal motor and it's gonna be really loud.

This is a generalization, of course, YMMV.

[Glen Blanchard]

I just went to buy some, but the Tiger link says they are no longer for sale? Does anyone have a good link to buy these logitech NC earphones Bob is raving about He convinced me.

Well, they are indeed very nice for that price. I wear them in the shop all the time. The sound from my iPod is great. I bought 2 pair and like them so much now that I would like to have some back stock. I bought mine from TigerDirect, and you are correct, they apparently no longer stock them. They are available on Amazon, but the once low price of $39.99 is now up to about $150. I am trying to watch the price a few times per week, as I would like to buy a couple more.

[Bryan Parlor]

The type of electric motor in a device has a major effect on the frequency and intensity of the noise produced.

Ever notice that devices with small motors (vacuum cleaners, SCMS, hand-held belt sanders, hair dryers etc.) tend to be loud screamers, whereas stationary devices, (TS, jointers, Dust Collectors, etc) tend to have a low pitch (almost a pleasant sound, IMHO) and are not nearly as loud?

This has to do with the type of motor used in the application. Cheap, portable devices use Universal motors. These are light, cheap, small, and put out a lot of power for their size. They also are noisy like nobodies business.

The term 'Universal' is applied to a series connected motor; one in which the same current passes through both the armature (rotor) and field (stator). The power source can be either AC or DC, hence the name universal or series universal.

Expensive, stationary devices use Induction motors. Induction motors are expensive, large, heavy, and quiet.

An induction motor (IM) is a type of AC motor where power is supplied to the rotating device by induction. An electric motor converts electrical power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a DC motor this power is supplied to the armature directly from a DC source. But in an AC motor this power is induced in the rotating device. An induction motor can be called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. Induction motors are widely used, especially polyphase induction motors, which are frequently used in industrial drives.

To see what I mean look at your 2.5 HP router. The whole thing smaller and lighter than just the 2 HP motor on your table saw. Yet, when you turn them on the difference in sound pressure is dramatic.

Therefore the general rule of thumb is; if you can lift it, it probably has a Universal motor and it's gonna be really loud.

This is a generalization, of course, YMMV.

Carl,
I suspect its the gearing that causes most of the noise on universal electric motors. If it has a cooling fan that could be a noise source as well.

I spinning rotor with cheap sleeve bearings should not generate much noise - bearing noise suggests rapid wear.

Bryan

[Bill Wyko]

I hate to be the Db dog but I've been it car audio for about 20 years. I've built sound systems that test as high as 176.5db. I made the mistake when I was much younger of playing systems way too loud. I now have high pitch ringing in my ears that will never go away. It makes some people go crazy. I just tell myself it's my internal turbo chargers. I strongly recommend protecting your ears unless you want to get internal twin turbos like mine. Once it happens it'll never go away so please be careful.

[Carl Fox]

Carl,
I suspect its the gearing that causes most of the noise on universal electric motors. If it has a cooling fan that could be a noise source as well.

I spinning rotor with cheap sleeve bearings should not generate much noise - bearing noise suggests rapid wear.

Bryan

Universal motors also have brushes which contact the communicator, which I'm sure is a major noise source. And a source of black dust as well.




Induction motors are brushless, so they are very quiet. Induction motors generally have built-in cooling fans as well so that can't be it unless the univerals use a different, noisier design. I imagine the heavier cases help as well.