The volume
control section starts with a volume meter that displays the current
volume as received from the soundcard. In intervals of 1/10 seconds,
the peak value of the input signal is measured and displayed as a
horizontal bar graph. Usually, the input level is displayed on a
logarithmic scale in dB. A value of 20dB increases the audio level as
measured in mV by a factor of 10; 6dB corresponds to a factor of
2. Negative values decrease the volume, hence -20dB is 1/10th of the
input level. The unit level 0dB is set to the maximum number that can
be represented as 16 bit signed integer. This is the maximum value
that can be represented with 16 bit audio data. The logarithmic scale
is used because equal differences in dB corresponds to equal
differences in perceived loudness. As an example: the difference in
loudness between -20dB and 0dB is roughly the same as the difference
between -40dB and -20dB. If the voltage level at 0dB corresponds to
32000, the voltage level at -20dB corresponds to 3200 and at -40dB
only to 320. In the first case the difference in level is about 29000
in the second case only 2900. If the absolute level is of interest,
pressing the button labeled "Lin" will switch the display to
linear. The button labeled "Log" can be used to switch back to
logarithmic scale (see also: linearscale).
The second pair of buttons labeled "Out" and "In" are used to
switch the scale between input and output level. This feature is
useful in conjunction with volume compression (see also: inputscale).
With the check box that comes next, you can enable automatic gain
control. If the box is checked, m3w will try to adjust the volume
control of your soundcard such that the level of the input signal is
neither too high nor too low. The details of automatic gain control
are explained in the volume control dialog section.
With the second check box, you can enable volume compression. If
the box is checked, m3w will try to increase the volume of the sound
data coming from your soundcard such that the level of the input
signal stays on a more ore less constant level. The details of volume
compression are explained in the volume control dialog section.
If volume
compression is enabled together with the display of the "Output"
level, the scale becomes a moving scale. While the full length of the volume
bar, as before, indicates full input level, the scale is adjusted to
reflect the current compression level. On this scale you can read of
the level of the output signal.
The space for the volume meter as part of the main dialog is very
limited. Hence the bars are very small. To get a bigger volume meter,
you can detach the meter display from the main dialog either using the
options menu, or by a simple double click on the meter display. Then a
volume meter like this will appear:
You can switch back to the small, attached display using again the
options menu, or by simply closing the meter window. While you have a
separate meter window, you can resize it to fit your needs.
The volume bar is divides into several sections indicating
different volume regions as determined by the settings in the volume
control dialog.
Noise Level
The dark blue part is the level below the "Noise Level". If
correctly adjusted, the level indicator should be at the right end of
the dark blue region if there is absolute silence. Only distortions by
the equipment or background noise is responsible for the measured
audio level.
Low Level
The normal blue section that follows indicates low input level. If
the auto gain feature is enabled, m3w tries to move up the mixer
setting to get the volume up.
Normal Level
The light blue section indicates normal level. As long as the
level is within this range, the auto gain feature will neither move
the mixer control up nor down.
High Level
When the color of the bar turns yellow, this signal is in the high
level region. If that occurs more than occasionally, automatic gain
control will start lowering the mixer control. To get the volume as
received from the soundcard back into the normal range.
Clipping
If the input level reaches the absolute maximum value, the input
volume is truncated by the soundcard to fit into the available 16
bit. This will cause audible distortion. To indicate clipping, a read
clipping indicator is displayed whenever that occurs.
The volume
control section starts with a volume meter that displays the current
volume as received from the soundcard. In intervals of 1/10 seconds,
the peak value of the input signal is measured and displayed as a
horizontal bar graph. Usually, the input level is displayed on a
logarithmic scale in dB. A value of 20dB increases the audio level as
measured in mV by a factor of 10; 6dB corresponds to a factor of
2. Negative values decrease the volume, hence -20dB is 1/10th of the
input level. The unit level 0dB is set to the maximum number that can
be represented as 16 bit signed integer. This is the maximum value
that can be represented with 16 bit audio data. The logarithmic scale
is used because equal differences in dB corresponds to equal
differences in perceived loudness. As an example: the difference in
loudness between -20dB and 0dB is roughly the same as the difference
between -40dB and -20dB. If the voltage level at 0dB corresponds to
32000, the voltage level at -20dB corresponds to 3200 and at -40dB
only to 320. In the first case the difference in level is about 29000
in the second case only 2900. If the absolute level is of interest,
pressing the button labeled "Lin" will switch the display to
linear. The button labeled "Log" can be used to switch back to
logarithmic scale (see also: linearscale).