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Peak-to-peak help?
Old 15th August 2007
  #1
Gear Nut
 
mobaudio's Avatar
Peak-to-peak help?

Ok, I don't know if this is the right forum for this, but I'm losing my patience.

I've got a bunch of files to convert and the client sent a spec sheet.

Now, I'm not new at this engineering thing, but I'm freaking confused about this:

"4. The audio waveform of the recorded wave sound should have an amplitude of 0.5 dB (peak to peak) as shown in the waveform graph attached."

I know what peak to peak is, but we're talking about digital files for this, which means 0.5db peak to peak would be clipping. Right?

I'm wondering; should I just make the peaks -0.5dB and call it a day?

Anyway, I attached the .pdf in case someone feels froggy and can help me out with this one. If you don't want to help, that's cool; you may still want to read the .pdf.

Thanks in advance.

I
Attached Files
File Type: pdf ECF_Voice_Info.pdf (70.1 KB, 232 views)
Old 15th August 2007
  #2
Lives for gear
 
jupiter8's Avatar
 

When you work with floating point audio it is represented as values between 1.0 and -1.0. So all in all you have 2.0 amplitude units to work with. The way i read it is they want something that is 0.5 amplitude units. A quarter of full scale.

Not sure what that means in dB. Isn't -6.0 dB half the amplitude ? So - 12.0 dB is quarter amplitude. I just did a quick visual check in Cubase and -12.0 dB looks about right.

If that's what they mean,i have no idea but it kinda looks like it in that PDF. Can't you just call/mail them and ask ?
Old 15th August 2007
  #3
Gear Nut
 
mobaudio's Avatar
Thanks for replying, Jupiter8.

I could call them and ask, but I'm more comfortable being ignorant here than in front of a client.

Although... the more I look at things, I realize the spec sheet is from the manufacturer and I could call them and maybe talk to one of their tech people.

Your reasoning seems sound. That sure is a low level, though.

I
Old 15th August 2007
  #4
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jupiter8's Avatar
 

Quote:
Originally Posted by mobaudio View Post
I could call them and ask, but I'm more comfortable being ignorant here than in front of a client.
Or even worse,make the client look like an idiot.They tend to dislike that.

But then again you have to weigh that against the possibility that you send in messed up files. Dunno your relation to the client.

And that level is'nt that low. You only loose 2 bits so a 24 bit recording will use 22 bits. Can't imagine anyone ever noticing that. How mp3s perform on low levels,i don't know though.
Old 15th August 2007
  #5
Gear Nut
 
mobaudio's Avatar
So I called the company. The woman answering the phone has no idea what I'm talking about.

BUT...

She sends an email to someone who can help. It's HIS day off and he winds up calling me in about an hour. He doesn't know the answer to my problem, but says he'll call the tech guy who WILL know.

After I explain that it's now too late and I sent the files, he asks if it's ok for the tech guy to call me back anyway. Sure, I say.

This whole time, they knew I am NOT a customer and I am NOT buying anything from them.

I am impressed with this whole exchange. Granted, they didn't get me the answer in time, but that's my fault. I've had the spec sheet for nearly two weeks, I coulda called earlier. Either way, that's some customer service. ESPECIALLY for a non-customer.

BTW- I went with -12dB peaks. If they send them back, I'll let you know.

And I will sue you.

I
Old 15th August 2007
  #6
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Goliath|Audio's Avatar
 

Doesn't really matter. You can have the peaks at any level you want. What really matters is the RMS values and the appearant loudness.
Old 16th August 2007
  #7
YZ!
Gear Addict
 
YZ!'s Avatar
 

The graph shown in the PDF is being grossly misinterpreted by whomever created the document.

the amplitude shown is not "0.5dB peak to peak" because this would represent a 1 dB dynamic range... and would show up as a straight line in the graph.

What the graph does show is a waveform that is peaking at 0.33 in a scale of -1 to 1.

(something in the neighborhood of -9 dB)

If your DAW supports showing this scale, just normalize the files to this level before converting to mp3 and you will be fine.

If it doesn't, try Audacity, freeware from Audacity: Free Audio Editor and Recorder

windows, mac, linux versions available.
Old 18th August 2007
  #8
Gear Nut
 
mobaudio's Avatar
Thanks for your input, everybody.

The tech guy called me and told me he never worried about the whole "peak to peak" thing. They were mostly concerned with the mp3 specs.

I got some sample files, and they were around -18dB RMS, so I made my files match that.

The tech also suggested I use Goldwave.

Oh well, the project is done, I got paid and I learned something.

I
Old 18th August 2007
  #9
Lives for gear
 
jupiter8's Avatar
 

Quote:
Originally Posted by mobaudio View Post
Thanks for your input, everybody.

The tech guy called me and told me he never worried about the whole "peak to peak" thing. They were mostly concerned with the mp3 specs.

I got some sample files, and they were around -18dB RMS, so I made my files match that.

The tech also suggested I use Goldwave.

Oh well, the project is done, I got paid and I learned something.

I
Cool.I was just going to post and ask how it all went.
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