Create an 80 db tone?

[Bearman]

Folks, I've used Audacity to generate a 1000 Hz tone of 50 ms duration in 44100 Hz/16-bit/stereo, but I don't know how to make sure that the tone is exactly 80 db. I've changed the verticle scale from "relative (1.0 to -1.0)" to "db" and it shows 0 to -96 db for the top half of each waveform and nothing for the bottom half. Anybody know to specify 80 db max??

Any advice appreciated!

thanks

[kozikowski]

You have two things going against you. The timeline only gives you waveforms down just so far and the generator level tools are terrible.

So.

Generate the tone to "1" (0 dBFS) and then use Effect > Amplify to drop it to whatever you want. You may need to do it more than once (two -40s, four -20s, etc.)

You'll be flying blind. Since technically, that's not "audio" any more (hearing goes away somewhere in the 60s), you'll just have to take their word on it.

You can take your work into a different Audacity and amplify it back up to prove that indeed, it's still there.

And I totally would not be doing this at 44100. That's a marginal delivery format, not a production or test format. 48000/16 (video format) or 48000/32 floating.

Koz

[alatham]

Your question doesn't make much sense the way you have it written.

Are you trying to make a waveform that peaks at -80dBs (Koz's post tells you how to do this)? Or are you trying to play a sound at exactly 80dB(SPL)?

Note that dB and dB(SPL) are two different units.

Decibels are a dimentionless unit and have no meaning without a reference point, it is impossible to make an audio file that will always play back at 80dB(SPL) (since there is no reference point to measure from). If you're trying to do that (to test room acoustics, or speaker placement, or something similar), then you need a Sound Pressure Level (SPL) meter. You'll have to generate your tone and then adjust the speaker volume while watching the SPL meter.

[kozikowski]

dBSPL is Sound Pressure Level. That measures the energy actually smacking the side of your head.

The other one is generally referenced to the point where the distortion goes to the moon because you exceeded the ability of the digital channel to carry it. That's clipping or reference to dBFS, or dB Full Scale.

Everybody uses the Radio Shack SPL meters, even if they don't admit to it. Even some of the big kids. The digital one is zippy, but impossible to take measurements that are changing--like audio. I have an analog one and the company owns a digital one.

http://www.radioshack.com/search/index. ... meter&sr=1

Koz

[Bearman]

Folks, thanks for all the advice. I wanted to make a tone that plays at exactly 80dB (SPL) via headphones. I've just used a Bruel & Kjaer audiometer and an "artificial ear" in order to measure the headphone output. The default tone produced by Audacity is just under 100 dB at the maximum volume, which makes sense. However, I've cut it down to 80 db using the "Amplify" function as suggested.

I'm very impressed with Audacity, works perfectly for generating the brief, simple tones that I need.