Poor Signal-To-Noise-Ratio Readings

摘要

AV9000 Checklist Item Under Test: 6.2.7: The electrical-noise levels for all audio channels are 55dB below the normal operating level for all audio sources. "Noise" refers to hum, electrostatic noise, radio-frequency (RF) interference, etc. Reasoning: For the most part, AV equipment is getting better and better with respect to noise levels. The AV9000 standard recommends systems have at least a 55dB signal-to-noise ratio (SNR) to assure that users don't hear any hiss or noise in the sound system when there is no signal present, but it's not uncommon to measure upwards of 70dB with today's equipment. However, when a problem does manifest itself, it's not enough simply to note that the system has a poor, nonconforming SNR. The team's needs are better met by spending a few minutes to pinpoint where, exactly, the problem is. It could be a noisy program source, a faulty microphone, poor cabling practices or even a necessary algorithm in the digital signal processor (DSP). Finding the source of the noise problem is far more valuable to the team than simply noting that a problem exists.