A Silent-Er Hazer

[TheSwami]

Searching back through the CB forums, it seems that, for a truly quiet hazer, the MDG Atmosphere series is cited as a go-to hazer in a number of threads, while the Ultratec Radiance is also spoken highly of in terms of noise output.

I've got an MDG Atmosphere with DMX remote. Our designer wants a very quiet hazer. As in, quieter than the MDG. He's worked with this theatre many, many times - normally, the hazer fan noise gets lost among the scroller fan noise in the catwalks, but for an upcoming performance, he wants the hazer under the deck (with an exposed frame), which puts it maybe 8-10' from the audience. As quiet as the MDG is (especially considering its output), when that output fan kicks on, it does make a little noise.

So, two questions:

1) Is there a quieter option than the MDG?
2) If not, any recommendations for muffling the MDG?

(A sound designer tried putting drier hose over the output fan of the MDG once - it caused dripping/condensing of the fluid and loss of output, and didn't really muffle the fan noise much. It was removed in short order. So that's right out.)

 

[TDN]

Isolate and box it. Try putting it up on some rubber pads, so it's vibrations don't transmit down into the floor. Then, build a big box around it, with one side open to let the haze out. Put rubber padding on the feet of the box. Line the inside of the box with fiberglass insulation and fabric. Try to have the opening of the box facing away from the audience. You want the box big enough to allow plenty of room for air circulation in and to fill it with absorptive material. It may not help enough, but should make an impact.

 

[LDTommy]

How old is your MDG? We have a few of them and they are all SILENT. Is is possible the fan is getting old and noisy? I've had one go bad in a 4+ old unit and had to have it replaced.

According to their website the units are 45.4 dB @ 1m, which I doubt anybody in the audience could hear.

 

[TheSwami]

Hmmm, that's a good thought, LDTommy - as far as I can tell from old records, the units about 8 years old (and predates me by many years). I'd be willing to bet the fan hasn't ever been replaced, I'll look into that.

TDN, thanks for the muffling advice! We'd thought about building a big insulated box, but isolating the hazer from transmitting vibrations to the floor directly wouldn't have been something I'd have thought of; we'll try padding underneath the hazer and the box as well.

A local vendor of ours suggested experimenting with turning out ZR-44 down to its lowest level and trying that, both for sound and to see if it better replicates the effect our designer wants (mist rising up from under the stage). I'll report back after some tests this weekend.

 

[Dalamar]

Well, first off, A unit without a pump will always win the battle against one with a pump. No moving parts = no mechanical noise.

Define the nature of the noise. The fan's revolution at full has a higher pitch in the 5-6kHz range but at a very low noise level, while too high a gas pressure will produce a higher -frequency hiss along with an audible, persistent and sharp turbulence swashing in the 300-1600Hz range. Both can be mitigated and quieted when placed behind soft goods (legs) and higher up in the theater box, far from the audience and the usual microphone pick up range.
Frankly, to hear ~46 db@ 1m (that's fan at full, while unit at full output, which the ATM is rarely used at) you have to be quite near.

If your ATM is noisier, you ought to have someone take a look at it. Make sure is it clean (no muck on the fan) , though I have serious doubts it would affect noise level. Oftentimes, a good factory clean-up is just what the doctor recommends for any and all ills after 8 years of uninterrupted service.