Audio level meter
A circuit for correcting the output of an audio level meter comprises input means for generating the square or the absolute value of an input signal, a low pass filter having a predetermined attack time and release time, and output means for converting the output signal from a linear scale to a logarithmic scale. The circuit further comprises a correction means to which an information about whether the input signal to the audio level meter was subject to squaring or converting into an absolute value at the input, as well as the attack and release time of the low pass filter, are supplied as input values, and which provides, at its output, a value representing the difference between the output of the audio level meter and the true signal power of the input signal.
1. Circuit for correcting the output of an audio level meter comprising input means for generating the square or the absolute value of an input signal, a low pass filter having a predetermined attack time and release time, and output means for converting the output signal from a linear scale to a logarithmic scale, characterized in that the circuit further comprises a correction means to which an information about whether the input signal to the audio level meter was subject to squaring or converting into an absolute value at the input, as well as the attack and release time of the low pass filter, are supplied as input values, and which provides, at its output, a value representing the difference between the output of the audio level meter and the true signal power of the input signal.
2. The circuit of claim 1 , further comprising means for adding the value representing the difference between the output of the audio level meter and the signal power of the input signal to the output value of the audio level meter.
3. The circuit of claim 1 , further comprising means for multiplying the output of the low pass filter with a correction value determined from the value representing the difference between the output of the audio level meter and the signal power of the input signal prior to converting the value into logarithmic scale.
4. The circuit of claim 1 , wherein the correction means comprises a look-up table holding values representing the difference between the output of the audio level meter and the signal power of the input signal for a number of ratios of attack and release time of the low pass filter and for input means forming the absolute value of an input signal and/or input means squaring the input signal.
5. The circuit of claim 4 , comprising an interpolation means for interpolating values for those ratios not included in the look-up table.