When you get down to 128kbps (the “near-CD” quality beloved of mp3 file purveyors on the internet) even my old ears can tell the clear difference between that and 192 and higher.
I think you’d have to have an extremely good ear and absolutely top-of-the-range audio equipment to notice any significant difference between the source (1411kbps) and 320kbps – and possibly as far down as 160kbps (iTunes suggests 160 or 192 for most purposes). Here are some of the results (the column tabulation may not show as it should): I made several mp3 versions of the sample at different bit rates, using eRightSoft’s “SUPER ©” media converter, and compared the spectral frequencies of these mp3 files on screen using CoolEdit. Using CoolEdit’s spectral frequency analyzer the frequency and harmonic content of the music was very obvious on screen. I copied the extract onto my computer using standard audio properties - bit rate 1411kbps, audio sample rate 44kHz, audio sample size 16 bit, and 2-channel stereo. I chose this because the harmonic content of her playing on her Guarnerius violin on occasion extends beyond 20kHz (about the top limit for a quality CD), and her playing is accompanied by a full classical orchestra. For my source I used a few seconds of a CD recording of the violinist Sophie Mutter playing part of Mozart’s A-major violin concerto. You may not be aware of this frequency loss if you’re listening on low-end audio equipment, but it is very definitely there.įor my own interest I’ve done a little research into this effect. Mp3 is very convenient for this but is what is known as a “lossy” format – which means the price you pay for a compressed file size is a loss of frequencies throughout the audio spectrum of the recording. Most of us at some time or other convert an audio recording to the more compact mp3 format for storage, or for play-back on mp3 players, or for sending audio files through web-space.