On May 6, 2010, at 9:10 AM, stephen barncard wrote: > The audio level control on the mac is not "tapered" for audio. Physical > volume controls on audio gear use a LOG taper. Once in a while one will run > into a consumer product with a LINEAR taper volume control in the circuit - > and you will notice it - most of the level change will appear in the first > 30% of the taper.
Yikes! This is one of those "Be careful what you ask for" situations I think. Haven't soldered a pot since I made shortwave radios and listened to Voice of the Andes and Radio Moscow! I guess the simple answer, for me at least, is "Listen to the sound and adjust by ear" - don't trust numbers. YMMV As for playing audio, I'm going to explore afplay, and some other options. OS X 10.5 includes a command line audio player (in /usr/bin) called afplay. This is very useful if you want to play a sound file from the command line, shell script, Automator action, etc. The /usr/bin directory is in your path by default, so you can just type afplay file.mp3 to play that file. afplay makes use of Core Audio, so I think it can play any audio file that QuickTime supports (including mp3, aiff, wav, etc.). There's a very simple man page for afplay, which then tells you that help is available with afplay -h. There are a few interesting options, including the ability to play a defined (in time) segment of a file, and to play a file to a defined audio output device. Thanks for the quick answers! sims The following is for the List Archives, just in case someone else is exploring the issue some day. -------- The List Archive is your friend ------- http://www.geofex.com/article_folders/potsecrets/potscret.htm The human ear does not respond linearly to loudness. It responds to the logarithm of loudness. That means that for a sound to seem twice as loud, it has to be almost ten times the actual change in air pressure. For us to have a control pot that seems to make a linear change in loudness per unit of rotation, the control must compensate for the human ear's oddity and supply ever-increasing amounts of signal per unit rotation. This compensating resistance taper is accurately called a "left hand logarithmic taper" but for historical reasons has been called an audio or log pot. In these pots, the wiper traverses resistance very slowly at first, then faster as the rotation increases. The actual curve looks exponential if you plot resistance or voltage division ratios per unit of rotation. If you used an audio/log taper pot for the control of the power supply we mentioned, the output voltage would increase very slowly at first, creeping up to maybe 10% of the final output at 50% of the pot rotation. It would then blast the other 90% in the last half of the rotation - very hard to control. Likewise, if we used a linear pot for volume control, the volume would come up dramatically in the first half of pot rotation, and then do very little change in the last half. -------- http://en.wikipedia.org/wiki/Potentiometer Potentiometers are widely used as user controls, and may control a very wide variety of equipment functions. The widespread use of potentiometers in consumer electronics has declined in the 1990s, with digital controls now more common. However they remain in many applications, such as volume controls and as position sensors. Linear potentiometers ("faders") One of the most common uses for modern low-power potentiometers is as audio control devices. Both linear pots (also known as "faders") and rotary potentiometers (commonly called knobs) are regularly used to adjust loudness, frequency attenuation and other characteristics of audio signals. The 'log pot' is used as the volume control in audio amplifiers, where it is also called an "audio taper pot", because the amplituderesponse of the human ear is also logarithmic. It ensures that, on a volume control marked 0 to 10, for example, a setting of 5 sounds half as loud as a setting of 10. There is also an anti-log pot or reverse audio taper which is simply the reverse of a log pot. It is almost always used in a ganged configuration with a log pot, for instance, in an audio balance control. _______________________________________________ use-revolution mailing list [email protected] Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-revolution
