Normalizing Music?

Beans asks: "I have a couple classical music CD's which I listen to at work, and use for putting the baby to sleep. I can never find the correct volume, I can't hear soft spots, so I turn it up, only to have a rising crescendo rouse the baby, or at work, have co-workers glace over. What is a good way to normalize them (read on for what I mean by normalize)? All of the normalizing software I have seen uses the entire song for the window of normalzing. Basically makes determines a static value required to get the average volume of the song to the user defined level, then applies that value to the entire song. What I need is something that normalizes over a sliding window, or say 5 seconds, or whatever. In effect making soft spots louder, and crescendo's quieter. Not the way the music was intended to be heard, but perfect for music-at-work, or putting kids to sleep. Does anyone know of any software that does this? On a side note, I work for a Seismic processing company, and we do stuff like this all the time on Seismic waves, not sound waves. If I can't find any canned software to do this, I may modify some of our code to work with WAV files, but I don't want to reinvent the wheel."

Comments

(-1 Flamebait)

[Knights who say 'INT]

You want quiet, listen to Enya. But don't go around raping the masters because of mundane utilitarian reasons.

Use your stereo's natural clipping ability

[Anonymous Coward]

What you need to take advantage of is called "clipping" by sound experts.

Let's say your stereo can play a waveform that varies between -1.0 and 1.0. If you send it a peak of +/- 2 for instance, it will clip to +/- 1.

What you need to do is find the lowest peak in your music. Even the "silent" parts have a little noise.

Let's assume that it goes +/- 0.01 in those parts. Find the recipricol (1/0.01) = 100 and set your gain to that.

The quiet parts will range +/- 1, and the loud parts will be clipped to also be +/- 1. Voila! You've "expanded" and "compressed" without all that fancy professional equipment.

Note: if you don't have an easy way to estimate the gain you need, just use a round estimate like 1000. You can find op-amps at your local Radio Shack that will amplify even higher than this! Just be sure to leave off the "feedback" part of the circuit. We all know that feedback is bad, right?

And as an added advantage, your child will grow up with a love of music by the Japanese artist Merzbow. It's a win-win-win.

Re:Classical != Quiet

[spaceyhackerlady]

It is just that there is a whole section of classical/trad music just for lulling babies to sleep. It is called a lullaby. While some of them have disturbing lyrics the baby doesn't care.

Benjamin Britten had something to say on the subject (A Charm, Op. 41):

Quiet!
Sleep! or I will make
Erinnys whip thee with a snake,
And cruel Rhadamanthus take
Thy body to the boiling lake,
Where fire and brimstones never slake;...

A few years ago my Mum was practising this before a concert (she's an accomplished musician) and heard a little girl, shaking, ask her Mum afterwards "Sh-sh-sh'e's k-k-kidding, isn't she?"

...laura

Low tech

[k4_pacific]

The low tech solution is to wire a small light bulb in series with your headphones. As you may know, electrical resistance increases with temperature. Thus, when the sound is louder, and more current is flowing to the headphones through the lightbulb, the filament gets hotter and glows brighter. This increases the resistance which limits the current flow and softens the louder sounds. Conversely, during quieter periods, there is less current, the lamp filament does not get as hot, and more current flows, making them louder.

Similarly, you can increase the dynamic range of the sound by putting the bulb in parallel to your headphones. Loud sounds increase the temperature (and thus the resistance) of the bulb filament, which diverts more current through the headphones. Quieter sounds don'y heat the filament as much and allow more current to take that route, thus making them even quieter.

You may have to experiment with different types of lamps to find which works best.