generating tones

[jane2978]

i have to generate pure tones. for this purpose, i am using the Generate -> Tone feature. the parameters that i am using are as follows.
1. waveform: sine
2. Hz : 440.00
3. amplitude: 1.0
4. length: 1.0

my question is regarding the audio track controls to the left of the waveform display. in particular, the gain control can set the dB from -36 dB to +36 dB. what if i need something outside this range? for example, i need to generate pure tones in the range -10 dB HL to 140 db HL. i am not sure what dB scale (suffix or reference level) the gain control is using. apparently, according to this article, http://en.wikipedia.org/wiki/Decibel, there are many types of dB suffixes and reference levels.

here are my questions.

1. what is the suffix or reference level of the dB for the gain control?
2. may i generate pure tones in the range from [-10, 140] db HL?

your help is appreciated. thank you in advance.

[kozikowski]

The dB in Audacity refers to the audio level where "0" is the maximum -- the place where the system cannot get any louder -- it runs out of numbers. The measuring system goes down from there to the "quiet" limit of system used -- it runs out of numbers the other way. For 16-bit sound, the lower limit is -96dB.

The volume slider refers to changes only. It's not absolute. Boost or cut up to 36dB from wherever you are now. That control is a little magic. You're better using Effect > Amplify to get predictable, statistical changes.

dB HL is a measurement for hearing and depends on the audio amplifier and headphones used. It works on calibrations external to Audacity. It's a remote cousin to dB-SPL Sound Pressure Level -- except it takes into account response variations of human hearing.

http://www.hearingoffice.com/download/DPgram.pdf

Koz

[steve]

Koz has covered about everything there, but just to fill in a bit of detail that you didn't ask...

1. what is the suffix or reference level of the dB for the gain control?

The gain slider on the left side of the track (in the "Track Control Panel") is, as Koz said, up or down from whatever the track currently is.
Most dB settings in Audacity refer to "dBFS" (dB relative to "Full Scale"), where "Full Scale" refers to both the track height (+/- 1.0) and to the 0 dB level on the recording/playback meters.
So for example, if you have a sine tone that goes up and down between +/- 0.25 (vertical height) on the track, that will measure as about -12 dB on the playback meter (with the gain slider set to 0).
If you push the track gain slider up to +6 dB, then the waveform in the track remains the same (totally unchanged), but the track will play +6 dB louder, so it will measure as about -6 dB (+6 dB up from the previous -12) on the playback meter.
How loud it sounds when you listen to it depends not only on how "loud" Audacity is playing, but also on how high your amplifier/headphones/speakers are turned up. So as Koz said you need a calibrated system to set the dBH level.

If you have perfect hearing, then you can make a very rough calibration by setting the playback level so that you just can/can't hear anything. This will be you 0 dB reference. A 6 dB increase in the level from Audacity will then correspond very roughly to a 6 dB rise in the playback level, but note that consumer grade mplifier/headphones/speakers are not linear, so the correlation will be very rough.

For measuring dBHL (accurately) you need a properly calibrated audiometer. Some info in these links:
http://en.wikipedia.org/wiki/Minimum_audibility_curve
http://en.wikipedia.org/wiki/Audiogram
http://en.wikipedia.org/wiki/Decibel