Anyone take more detailed noise measurements?

[AndrewQ]

I've seen people reporting overall dB levels, but does anyone have any more detailed measurements? Specifically, a noise spectrum (frequency vs amplitude)? If so, I would be very grateful if you could share it.

I'm strongly considering buying a clearvue, but I will have to make it quieter to use it in my basement shop. I've seen the mufflers that people have built along with the enclosures (closets). I have a few years experience in that field and I have a few ideas on how to improve on these ideas but it's all frequency dependent. So, if anyone has data, I would appreciate it. Thanks.

Andrew

 

[bababrown]

Andrew,
Do a search on "jgveill" and you will find a frequency analysis. I know someone later did an FFT using an iPhone but I haven't found it.
bababrown

 

[AndrewQ]

Thanks bababrown. I found a few attachments that contained frequency info. There's a lot of variation, but that's not too surprising considering all the variables.

I was surprised that the noise wasn't more tonal, but it still looks like the primary blade pass frequency and the first harmonic are the highest peaks. There's also lot of broadband noise but I assume that's mostly aero noise. I'm not sure what the source of the low frequency noise is, but the room itself is probably being excited in some of these measurements.

 

[Mike Goetzke]

Thanks bababrown. I found a few attachments that contained frequency info. There's a lot of variation, but that's not too surprising considering all the variables.

I was surprised that the noise wasn't more tonal, but it still looks like the primary blade pass frequency and the first harmonic are the highest peaks. There's also lot of broadband noise but I assume that's mostly aero noise. I'm not sure what the source of the low frequency noise is, but the room itself is probably being excited in some of these measurements.

If I had the time I was always thinking of trying a Helmholtz Resonator on the outlet of the cyclone.

Mike

 

[AndrewQ]

If I had the time I was always thinking of trying a Helmholtz Resonator on the outlet of the cyclone.

Mike

I agree Mike, my initial plan was a Helmholtz (or a quarter wave) tuned to the primary blade pass frequency, but the noise data I found showed the first harmonic was almost as loud. Helmholtz's need to be tuned to a relatively narrow frequency to be effective. Of course two could be used, but at that point it would make sense to consider a bandstop arrangement as an alternative. One challenge is comparing the backpressure of the various designs. Probably easiest to build prototypes and test them as opposed to comparing them analytically.

But the real issue is the cyclone will be too loud even if those frequencies are knocked down quite a bit. So a Helmholtz or two will help but won't be enough (assuming the freq data posted is representative of a typical installation). Handling the rest of the frequency range is tradeoff between space (volume) and backpressure.