## How to calculate Octaves/Minute

## How to calculate Octaves/Minute

(OP)

I am trying to figure out how to calculate octaves/minute for one of the shaker tests I am running. The original test request said that I needed to run a shaker test with a logarithmic Sine sweep from 10 to 2000 Hz and back to 10 Hz in a period of 20Minutes (10minutes/sweep). Now I want to change the log sine sweep from 10 to 200 Hz and back to 10 Hz (instead of 2000 Hz), now I want to find out what time it would have taken to go from 10 to 200Hz (had I swept it to 2000Hz in 10minutes). The software asks me to enter Octaves per Minute (instead of time) for new test requirement. Having a Master's in vibration I am a bit ashamed to say that I never seen this units of convention before in vibrations. Can someone help me how to figure out the octave per minute calculation(I somehow came to know it is about .764 for this particular case).

## RE: How to calculate Octaves/Minute

so

n log 2 =log 2000-log 10

so

n=(log(2000)-log(10))/log(2)

and similarly for the new sweep.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

## RE: How to calculate Octaves/Minute

n=(log(200)-log(10))/log(2)=4.321

considering it is 4.321 octave/sec

n would be .0720321 octave/minute

so where in the world .764 come from? Am I missing any more data?

## RE: How to calculate Octaves/Minute

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

## RE: How to calculate Octaves/Minute

So if they are 7.64 octaves between 10 to 2000 and I need it to sweep from 10 to 2000Hz in 10minutes, it needs to sweep at the rate of 7.64/10 octaves/minute=0.764octaves/minute and thats how I got the sweep rate

Got it. Thanks a lot for your help. I needed to know this though I already started the test I was trying to figure out where the number came from?

Thanks to your formula now its clear.

Can you tell me in which book can I find this formula and the derivation behind it. I would really appreciate it

## RE: How to calculate Octaves/Minute

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

## RE: How to calculate Octaves/Minute

20,40,80,160,320,640,1280 so they are 7+x Octaves right?

x should be less than 1 since octave of 1280 would be 2560 which is greater than 2000 so x should be a fraction leass than 1

but how do u get 'x' by this method

it can't be (1280)^x=(2000-1280)????

what is it then?

## RE: How to calculate Octaves/Minute

There's no 'easier' way, that's just how it works.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

## RE: How to calculate Octaves/Minute

Masters in Vibration and not understanding how to figure out octaves???? Ask for your money back!!!

## RE: How to calculate Octaves/Minute

## RE: How to calculate Octaves/Minute

Perhaps you could review your undergraduate texts.

## RE: How to calculate Octaves/Minute

Tom Irvine

www.vibrationdata.com

## RE: How to calculate Octaves/Minute

"Octave

An octave is a frequency interval having a ratio of two. It is called an octave from the music tradition where an octave spans eight notes of the scale. The second harmonic of a spectral component is one octave above the fundamental. In acoustical measurements, sound pressure level is often measured in octave bands, and the center frequencies of these bands are defined by the ISO. Vibration measurements are seldom expressed as octave band levels, but the US Navy has used 1/3 octave band analysis for vibration measurements on submarines for a long time. "

Source: http://www.vibinst.org/vglos_f-o.htm#o

I hope you know what a vibration institue is

I am not ashamed to say "I dont know when I dont know" b'cos being an engineer I know its always being on a learning curve. Octave is seldom used in vibrations its associated with acoustics, since a lot of times acoustics and vibrations go together, definitions are interchanged easily.