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Wayne A. Pflughaupt · 07-21-2003, 03:03 PM

Expanding on what David wrote:

In every room where the sound is well-balanced - the lows, mids and highs blend well, with nothing apparently exaggerated or lacking - there is a natural, upward tilt from the higher frequencies to the low (i.e., the low frequencies are at the top of the rise).

Put another way, although in-room response sounds flat, it does not measure flat. The higher frequencies will register lower SPL readings, while the lower frequencies will register higher readings - say, 65dB at 3,000Hz, and 73dB at 50Hz.

Since the lower frequencies have higher SPL readings, that is why the numbers “go off the scale” when you switch from A to C weighting.

Quote:

Also, when I switch to "c" weighting, and set the meter to 70db, I cannot calibrate at this level because the needle is pegged to the right. Could there be a problem with the meter?

There is nothing wrong with the meter – it is behaving correctly. The meter has a series of ranges in 10dB increments from about 60dB to 120dB. If you are reading off the scale, use the “Range” knob to select the next higher range.

Regards,
Wayne A. Pflughaupt