Noise Reduction / Attenuation
Noise attenuation states how much a defined noise component is reduced, expressed in decibels.
The result needs a frequency range, measurement method and operating condition. A single attenuation number does not mean equal reduction at every frequency.
Noise Reduction / Attenuation — Headphone
For headphones, attenuation can describe passive isolation, active noise cancellation or their combined measured result. Seal, fit and the type of surrounding noise affect performance.
Compare the same mode and test method. Passive and active figures should not simply be added, and a peak reduction at one frequency does not describe the entire noise spectrum.
Noise Reduction / Attenuation — Power Filter
For a power filter, attenuation describes reduction of specified electrical noise passing through the supply path. Frequency and the source and load impedances affect the result.
Compare the same noise mode, frequency range and test setup. Mains-frequency harmonics and high-frequency conducted interference are different phenomena; an attenuation figure alone does not establish an audible improvement.
Noise Reduction / Attenuation — Power Regenerator
For a power regenerator, attenuation describes reduction of a specified electrical noise component between the incoming supply and regenerated output. The test conditions identify what is being reduced.
Compare the same frequency range, load and noise definition. Keep conducted-noise attenuation separate from output waveform distortion, and do not read a single figure as uniform suppression of every supply disturbance.