Stuart's Audacity Tips 025 - Why Is dB Negative?

[@barbarahartigan1179]

Fantastic..I serached the entire internet and didn't understand this until you video! Thank you!

[@stuartsaudacitytips]

My pleasure; glad it helped.

[@TexpatOTG]

Enjoyed this. Always wondered. Cheers

[@stuartsaudacitytips]

Thanks! Glad it helped. Cheers!

[@dimtsel4044]

mm so the metrics of the sound in db are influenced by the the scale they are measured. That make sense now. Thanx for the tip Stuart.

[@stuartsaudacitytips]

Glad to help.

[@decodr-ring]

Hi Stuart, negative decibels is a difficult topic to explain, and I think an important concept was missed in this video. Decibels are a type logarithm (the value is 10 to the power of the decibels). So -2 dB is the square root of 10 which is a positive value between 0 and 1.0. Then -3 dB is the cube root of 10 which is a smaller fractional number, yet positive value. And 0 dB is the same as 10 to power 0 which equals 1.0. That’s called unity or Full Scale. The confusion for me was the question of how can there be negative sound? It helped me to learn all negative decibels represent fractions less than 1.0 that are positive values. You touched close to that concept by showing that the linear scale in Audacity is positive between 0.0 and 1.0. Cheers

[@stuartsaudacitytips]

Thanks for the comment. Yes, the entire subject of measurement can get quite lengthy and technical. I try to keep SAT "nerdy enough to learn something new" without getting too deep into the weeds, since most readers/viewers aren't extremely technical. There are other editions that deal with the dB scale, too (some haven't been made into videos yet), so check those out and stay tuned for more!

[@emilefeltesse]

Perfectly described 👌🏻

[@stuartsaudacitytips]

Thanks so much! I'm glad you found it to be helpful.

[@stephengray9207]

At the 4 minute mark, you said the volume doubles or halves with every 6db change BUT thats not correct, its every 3db.

[@stuartsaudacitytips]

Good catch! Not sure what I was looking at back then; I've removed that section. Episode 057 (kzbin.info/www/bejne/jYO0q3qLnZKFg6s) is a much more complete presentation of volume/perceived loudness, and has correct values. Thanks for the comment.

[@davidwright9940]

Hi, thanks for the video, really helpful. A silly question but why dose the waveform go both directions from the centre? If it's showing loudness why dose it not just go from one point and then up? Hope that makes sense.

[@stuartsaudacitytips]

Great question! Sound is caused by pressure changes moving through a medium (usually air, for humans). The waveform shows increases and decreases in pressure (called compression and rarefaction when we talk about gases like air); increases rise above the centerline and decreases fall below it. Silence is right in the middle, when no changes in pressure occur. Hope this helps!

[@davidwright9940]

@@stuartsaudacitytips Thank you for explaining.