These are the results from using one track only. It may, or may not, be representative, but the results are fairly interesting. I make no comment, I am posting for others to comment.
******** WaveGain, NO DITHER
D:\testdir>lame --preset standard 132.wav 132.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 132.wav to 132.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:35/ 0:35| 0:35/ 0:35| 6.0438x| 0:00
32 [ 151] ****
128 [ 790] %%***************
160 [2880] %%%%%********************************************************
192 [3157] %%%%%%%%%%%%%%%%%*************************************************
224 [ 803] %%%%%************
256 [ 247] %%****
320 [ 180] %***
average: 179.5 kbps LR: 1384 (16.86%) MS: 6824 (83.14%)
Writing LAME Tag...done
******** WaveGain, DITHER with NO NOISE SHAPING
D:\testdir>lame --preset standard 132.wav 132.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 132.wav to 132.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:36/ 0:36| 0:36/ 0:36| 5.9545x| 0:00
32 [ 150] %%%*
128 [ 801] %%***************
160 [2848] %%%%%******************************************************
192 [3201] %%%%%%%%%%%%%%%%%%************************************************
224 [ 782] %%%%%************
256 [ 240] %%***
320 [ 186] %%**
average: 179.5 kbps LR: 1520 (18.52%) MS: 6688 (81.48%)
Writing LAME Tag...done
******** WaveGain, DITHER with LIGHT NOISE SHAPING
D:\testdir>lame --preset standard 132.wav 132.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 132.wav to 132.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:36/ 0:36| 0:36/ 0:36| 5.9339x| 0:00
32 [ 14] %
40 [ 1] *
128 [ 916] %%%%****************
160 [2877] %%%%%*******************************************************
192 [3172] %%%%%%%%%%%%%%%%%%************************************************
224 [ 797] %%%%%************
256 [ 249] %%****
320 [ 182] %***
average: 181.2 kbps LR: 1534 (18.69%) MS: 6674 (81.31%)
Writing LAME Tag...done
******** WaveGain, DITHER with MEDIUM NOISE SHAPING
D:\testdir>lame --preset standard 132.wav 132.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 132.wav to 132.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:36/ 0:36| 0:36/ 0:36| 5.9831x| 0:00
32 [ 10] %
128 [ 916] %%%%****************
160 [2895] %%%%%********************************************************
192 [3156] %%%%%%%%%%%%%%%%%*************************************************
224 [ 810] %%%%%************
256 [ 245] %%****
320 [ 176] %%**
average: 181.2 kbps LR: 1485 (18.09%) MS: 6723 (81.91%)
Writing LAME Tag...done
******** WaveGain, DITHER with HEAVY NOISE SHAPING
D:\testdir>lame --preset standard 132.wav 132.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 132.wav to 132.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:36/ 0:36| 0:36/ 0:36| 5.9390x| 0:00
40 [ 1] *
128 [1115] %%%%%*******************
160 [3176] %%%%%%%%**********************************************************
192 [2890] %%%%%%%%%%%%%%%%*********************************************
224 [ 653] %%%%**********
256 [ 222] %%***
320 [ 151] %***
average: 177.5 kbps LR: 1583 (19.29%) MS: 6625 (80.71%)
Writing LAME Tag...done
******** ORIGINAL WAVE FILE + LAME --scale
D:\testdir>D:\testdir>lame --preset standard --scale 0.691 13.wav 13.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 13.wav to 13.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:36/ 0:36| 0:36/ 0:36| 6.0251x| 0:00
32 [ 152] %***
128 [ 810] %*****************
160 [2876] %%%%%********************************************************
192 [3130] %%%%%%%%%%%%%%%%%*************************************************
224 [ 815] %%%%%*************
256 [ 238] %%****
320 [ 187] %***
average: 179.5 kbps LR: 1372 (16.72%) MS: 6836 (83.28%)
Writing LAME Tag...done
******** ORIGINAL WAVE FILE + LAME AS REFERENCE
D:\testdir>lame --preset standard 13.wav 13.mp3
LAME version 3.90.3 MMX (http://www.mp3dev.org/)
CPU features: i387, MMX (ASM used), 3DNow!, SIMD
Using polyphase lowpass filter, transition band: 18671 Hz - 19205 Hz
Encoding 13.wav to 13.mp3
Encoding as 44.1 kHz VBR(q=2) j-stereo MPEG-1 Layer III (ca. 7.4x) qval=2
Frame | CPU time/estim | REAL time/estim | play/CPU | ETA
8206/8208 (100%)| 0:35/ 0:35| 0:35/ 0:35| 6.0544x| 0:00
32 [ 151] ****
128 [ 779] %****************
160 [2771] %%%%%*****************************************************
192 [3188] %%%%%%%%%%%%%%%%%*************************************************
224 [ 872] %%%%%**************
256 [ 251] %%****
320 [ 196] %%***
average: 180.6 kbps LR: 1373 (16.73%) MS: 6835 (83.27%)
Writing LAME Tag...done
D:\testdir>