# Extract the left channel from an mp3 file

I'm trying to control where a sound is going to be heard, in the left

For example, when I import an mp3 file, and I want to hear it only from the left ear, what should I do?

I've never worked with sounds before, so I didn't know where to start. The Documentation Center seems very undocumented on this topic.

• MMA does not have native mp3 import. You'll need to convert it into a supported format, then import, and you can then manipulate it.
– ciao
Feb 22 '14 at 10:53
• And can't the mp3 be converted inside MMA? Also, what formats are you talking about? Feb 22 '14 at 10:57
• You could, I suppose, convert it in MMA, but there are far easier ways, including open-source. Search the doc. center for "sound", see the "sound and sonification", "the representation of sound", "audio formats", and the tutorials therein.
– ciao
Feb 22 '14 at 11:01
• The supported formats for sound import are here Feb 22 '14 at 13:04
• @Arcotick so if you solve the issue with the supported formats, do I understand you correctly, that you want then extract just a channel from that stereo sound? for instance left channel is voice and right channel guitar. you want to extract the voice channel into a mono? Feb 22 '14 at 14:55

The first step is to convert the sounds to one of the supported formats. I recommend WAV or FLAC. Then you can Import it. You'll get an expression of the form

Sound[SampledSoundList[{leftChannel, rightChannel}, sampleRate]]


where rightChannel and leftChannel are numerical lists of amplitudes.

Generally, if you want to hear the sound from just the left speaker, you need to create an all-zero amplitude list of the same length for the right channel too.

For example, after extracting data from the above expression, you can re-create it as

Sound[SampledSoundList[{leftChannel, 0*rightChannel}, sampleRate]]


to mute the right channel.

• i thought more of something like: Sound[SampledSoundList[sound[[1, 1, channel]], sample_freq]]. totally overseeing the muting effect by multiplying with zero ;) Feb 22 '14 at 18:46
• @Stefan Yours is the way to go to extract one channel. But as I understood the question the OP wanted the sound to come only from the left channel and not the right one, hence the need for an all-zero right channel. Feb 22 '14 at 23:09