So, when using different volume scales, the numbers might not reflect the same sound intensity as the THX reference level. However, with other volume scales, the numbers on the scale may not directly correlate to the THX reference level or the dB scale. When using a THX-certified amplifier or receiver with the -dB scale on the volume control, 0dB represents the THX reference level, which corresponds to an average SPL level of 85dB with a typical +/- 20db swing in peaks. However, for audio processors that are THX-certified and/or running Audyssey room correction, the tones will be emitted at 75dB, which is corrected internally to correspond to 85dB. However, some general guidelines can be followed to achieve a balanced and realistic sound reproduction while calibrating or measuring your audio system.Īccording to the THX standard, which is a set of specifications for high-quality audio-visual systems and is the standard when calibrating home audio, the reference dB level for a home theater system should be 85dB for each speaker when playing pink noise test tones. The optimal dB level for a home theater system depends on personal preference and listening environment. So, if a 30Hz tone is played at the same dB(Z) level as a 1000Hz tone and we switch to dB(A) weighting, we will notice that the dB(A) level of the 30Hz tone is much lower than the 1000Hz tone. For instance, humans are less sensitive to lower frequencies than to higher ones. Graph showing the weighting differences between dB(A), dB(C), and dB(Z).Įach weighting has a specific adjustment used to align measured sound intensity with how humans perceive it. The dB(Z) unit is used to express sound pressure levels measured with the Z-weighting filter. It is equivalent to measuring the sound level in decibels (dB) without any weighting filter. The dB(C) unit is used to express sound pressure levels measured with the C-weighting filter.ĭB(Z): The Z-weighting filter is also known as the zero-weighting filter, because it does not apply any frequency correction to the measured sound pressure level. It is more suitable for measuring peak sound levels, such as home audio or rock concerts, where the human ear becomes less sensitive to frequency differences. The dB(A) unit is used to express sound pressure levels measured with the A-weighting filter.ĭB(C): The C-weighting filter is similar to the A-weighting filter, but it attenuates lower and higher frequencies less than the A-weighting filter. It attenuates lower and higher frequencies more than mid-range frequencies, which are the ones that humans hear best. There are three main types:ĭB(A): The A-weighting filter is the most commonly used when measuring environmental sound, and it mimics the human ear’s response at moderate sound levels. To account for this frequency-dependent perception of loudness, a weighting filter is usually applied to the sound pressure level measurements. We explain this concept in further detail in our article “ Understanding Audio Dynamic Range.”

This means that a sound with a constant intensity across all frequencies will not sound equally loud at different frequencies. The ear is more sensitive to mid-range frequencies (around 1kHz to 4kHz) than to lower or higher frequencies. However, the human ear is not equally sensitive to all frequencies of sound. The human ear can perceive a wide range of sound pressures, from the threshold of hearing (about 0dB) to the threshold of pain (about 120dB).

However, it is essential to interpret decibel measurements with consideration of the reference level and the specific weighting used (e.g., A-weighting and C-weighting) to accurately understand the impact of sound on human perception. It enables us to assess sound exposure, and to ensure proper audio balance for a better listening experience. The decibel scale is commonly used to measure sound levels in various contexts, such as home theaters, concert venues, industrial settings, and even environmental noise monitoring.

Decibels logarithmic scale