Tech: Setting a wav file to be 15dB?

Subject: RE: Tech: Setting a wav file to be 15dB?
From: pdq
Date: 12 Mar 06 - 10:14 AM

1/2 of the output level would be "6dB down" or -6dB or 50%

1/4 of same would be "12 dB down" or -12dB or 25%

1/6 would be "15.56 dB down" or -15.56 dB or !=16.66%

          1/6 is probably what you are looking for...try it and find out?

Subject: RE: Tech: Setting a wav file to be 15dB?
From: Dave the Gnome
Date: 12 Mar 06 - 08:19 AM

Aha! Found some help on the Mitel switch page - It suggests using Cooledit 2000 and gives the following instructions -

Click Transform, click Amplitude, and then click Amplify.

After the Amplify window opens, click the 'View All Settings in db' check box. Click the Constant Amplification tab and type -15 in the 'dB' text field.

So.

It is indeed -15 (Although in truth the instruction was split with the '-' on one line and the 15 on the next so it wasn't easy to spot. That's my excuse anyway:-) )

Them were words of more than one syllybub, Bernard! But I think I'm begining to get the picture. On WavePad it gives percentages so If I take it to, for instance, 25%, of the original how many dBs would I be reducing it then? Or is it not that easy?

It may take me a while but I'll get there eventualy...

:D

Subject: RE: Tech: Setting a wav file to be 15dB?
From: The Fooles Troupe
Date: 11 Mar 06 - 06:31 PM

Dave the gnome,

The previous discussion was on electrical levels in dB.

With regard to 'loudness' as in aural loudness - the dB 'level' that are quoted eg 100bB, etc is still a relative term.

Subject: RE: Tech: Setting a wav file to be 15dB?
From: The Fooles Troupe
Date: 11 Mar 06 - 06:23 PM

Thanks Bernard - couldn't remember the magic number! And had guessed it was propbably meant to be a negative number.

Subject: RE: Tech: Setting a wav file to be 15dB?
From: Bernard
Date: 11 Mar 06 - 08:43 AM

In audio recording terms, 0dBU is taken as the reference point, and equals 0.775v RMS.

+15dB would be horribly distorted due to 'clipping' with most audio equipment, so this instruction probably means -15dB.

By my reckoning, -15dBU is around 0.14v RMS or 0.39v peak-to-peak. Approximately, of course...!!

For comparison, 0dBV is 1v, and is often the standard used in live mixing desks.

'Clipping' occurs when a signal is too strong for the input, and so called because of the appearance of a 'clipped' sine wave trace on an oscilloscope.

A sine wave should have smoothly curved peaks and troughs, but a clipped sine wave literally has the peaks and troughs chopped off at the point where the input device is overloaded. This is why the sound is distorted.

This website shows clearly what the problem is... although the author is using it to demonstrate how to get an 'interesting' sound!

Each to their own...!

Subject: RE: Tech: Setting a wav file to be 15dB?
From: Snuffy
Date: 11 Mar 06 - 07:15 AM

As I remember from a brief exposure to electronics in the late 60s a dB is a measure of ratio. 6dB ="double", so 12db=4 times as much, 18db = 8 times as much, 24db = 16 times as much, etc.

So if you ordered +15dB relative to a pint of beer you'd get about 6 pints, but relative to a gallon you'd get 6 gallons.

Subject: RE: Tech: Setting a wav file to be 15dB?
From: Dave the Gnome
Date: 11 Mar 06 - 05:45 AM

Thanks peoples - Don't understand a couple of points:-(

Fullerton - I have used a software compressor (I think) - WavePad. Does Audacity have the ability to output a wav file that will play at 15dB. Bringing me onto my next question...

Foolestroupe - Don't understand that at all. 15dB isn't relative to anything is it? Isn't 15dB a measure of 'loudness' - like 15cc is a measure of volume or 15 grams a measure of weight? I assume that when they say that the the wav file output needs to be set to 15dB they mean when it plays on a pre-determined device - In this case our telephone switch. Am I missing something? If so can you explain to me - Preferably in words of one sylable so I can understand it:-)

Bernard - may well take you up on your offer - I want to bring my concertina round for a dose of looking at anyway:-) Trouble is I will need to convert a few tracks so the rest of the crew can decide which one they want to use - And I will need to include some pop dross - Are you sure your equipment will not reject it;-)

Cheers

DtG

Subject: RE: Tech: Setting a wav file to be 15dB?
From: The Fooles Troupe
Date: 11 Mar 06 - 03:19 AM

"needs to be set to play at 15dB"

Relative to what?

Subject: RE: Tech: Setting a wav file to be 15dB?
From: Bernard
Date: 10 Mar 06 - 06:51 PM

Bring it round here, Dave - I've got Sound Forge.

Subject: RE: Tech: Setting a wav file to be 15dB?
From: Fullerton
Date: 10 Mar 06 - 06:26 PM

Use a (software) compressor.
Free program audacity has a simple one.
It will do file conversion too.
Always use a a COPY of your original wav.

Subject: Tech: Setting a wav file to be 15dB?
From: Dave the Gnome
Date: 10 Mar 06 - 04:26 PM

Trying to replace our phone switch 'on hold' music with something better than the preset bongos! It says I need to have a wav file - done - set to certain criteria - done - no longer than 4 minutes - check and no bigger that 5Mb - OK. It also needs to be set to play at 15dB. I have experimented in Wavepad with 50% and 25% amplification but I am only guessing and the music is still distorted. Any suggestions on how to get it to exactly 15dB?

Cheers

DtG