#34: Levelling Your Peaks

The Question

Glenn from work Says:
April 8th, 2005 at 8:21 am

What criteria do cable companies use to determine where in the volume is the best stereo? It has to do if you put your audio through the digital cable box and the volume through that. Its pretty much different on each model of cable box.

Kurt – I have no idea what Glenn is talking about here, but I just typed it in.

The Answer

Well Glenn, the answer is related to several factors, including impedence, as well as the expected level that makes the best use of the hardware. Generally the manufacturer of the cable box will use a test tone (something like a sinusoid tone at 1 kHz) and ensuring that the tone registers somewhere between 12 and 18 decibels, they ensure that the box is likely to output the correct volume that matches closest to optimum as far as stereo goes. Different hardware most likely has different signal paths, which can produce different optimum volume levels.

Of course, it’s also fairly likely that there isn’t that tight quality control on cable box audio output, and that each company picks a set value and sticks with it. And since the industry isn’t really interested in sharing data between rival companies, it’s no wonder they didn’t pick the same volume. Ahh well.

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