Understanding Decibel (dB)
The decibel (dB) is an international standard unit used to compare sound, power, signal strength, and similar quantities. It is essential in nearly all audio-related fields, including audio engineering, acoustic design, music production, and hearing protection. The most distinctive characteristic of the decibel is that it uses a logarithmic scale. Human hearing is not linear; a tenfold increase in sound intensity is perceived as roughly twice as loud. Therefore, the decibel employs a logarithmic function to accurately reflect this perceptual property of human audition.
Decibel (dB)
The decibel is a unit used to compare relative magnitudes or intensities, primarily expressing ratios of power or amplitude. It is generally referenced to 0 dB as the baseline, where values above 0 dB indicate greater intensity or magnitude, and values below indicate the opposite. Decibels are widely used in music, audio engineering, and electronic devices.
In decibel formulas, the coefficient K depends on whether the comparison is based on power or amplitude. When comparing amplifier output or speaker wattage, use 10 × log (power ratio); when discussing sound pressure level (SPL), always use 20 × log (pressure ratio).
The decibel formulas are as follows.
$$ \text{dB} = K \times \log_{10} \left( \frac{\text{measured value}}{\text{reference value}} \right) $$
$$ K = 10 \quad \text{(for power, energy, or intensity comparisons)} $$
$$ K = 20 \quad \text{(for amplitude, sound pressure, voltage, or current comparisons)} $$
Perceived Loudness by Decibel Change
The decibel (dB) scale, due to its logarithmic nature, produces significant perceptual differences even with small numerical changes. Below are the perceptual experiences observed for key increments in professional audio contexts.
+3dB
A subtle level increase that is perceptually detectable but not dramatically noticeable in everyday listening or conversation. It corresponds to a volume adjustment of approximately one step on a typical headphone or amplifier control, resulting in a slightly richer and fuller sound without standing out prominently. In terms of sound pressure, this represents an amplitude increase of approximately 1.41 times (√2).
+6dB
A clearly noticeable level increase that feels nearly twice as loud. It corresponds to an exact doubling of sound pressure amplitude (quadrupling of power), creating a distinct sense of increased presence and clarity. In a quiet indoor environment, this is the difference between a conversation suddenly becoming more articulate and prominent upon someone entering the room.
+10dB
The most prominent perceptual change interval, where the sound is generally perceived as approximately twice as loud. It corresponds to an amplitude increase of about 3.16 times (√10) in sound pressure and exactly 10 times in power, resulting in a transition from quiet café conversation levels to noisy restaurant or street noise levels.
+20dB
A dramatic shift into an entirely different sonic dimension. It corresponds to a 10-fold increase in sound pressure amplitude and a 100-fold increase in power, making whispers feel like normal conversation and normal conversation feel like front-row concert levels. The change is so substantial that it is perceived as almost a completely different acoustic environment.
-10dB
Conversely, a reduction where the sound feels approximately half as loud. It corresponds to an amplitude decrease of about 1/3.16 times in sound pressure and 1/10 times in power, creating a clear sense of sudden quietness, as if the volume has been sharply lowered.
-20dB
The sound diminishes to an almost inaudible level. It corresponds to a 1/10 reduction in sound pressure amplitude and a 1/100 reduction in power, resulting in a faint whisper-like presence within a noisy environment.
Perceived Loudness by Decibel Change
The decibel (dB) scale, due to its logarithmic nature, produces significant perceptual differences even with small numerical changes. Below are the perceptual experiences observed for key increments in professional audio contexts.
+3dB
A subtle level increase that is perceptually detectable but not dramatically noticeable in everyday listening or conversation. It corresponds to a volume adjustment of approximately one step on a typical headphone or amplifier control, resulting in a slightly richer and fuller sound without standing out prominently. In terms of sound pressure, this represents an amplitude increase of approximately 1.41 times (√2).
+6dB
A clearly noticeable level increase that feels nearly twice as loud. It corresponds to an exact doubling of sound pressure amplitude (quadrupling of power), creating a distinct sense of increased presence and clarity. In a quiet indoor environment, this is the difference between a conversation suddenly becoming more articulate and prominent upon someone entering the room.
+10dB
The most prominent perceptual change interval, where the sound is generally perceived as approximately twice as loud. It corresponds to an amplitude increase of about 3.16 times (√10) in sound pressure and exactly 10 times in power, resulting in a transition from quiet café conversation levels to noisy restaurant or street noise levels.
+20dB
A dramatic shift into an entirely different sonic dimension. It corresponds to a 10-fold increase in sound pressure amplitude and a 100-fold increase in power, making whispers feel like normal conversation and normal conversation feel like front-row concert levels. The change is so substantial that it is perceived as almost a completely different acoustic environment.
-10dB
Conversely, a reduction where the sound feels approximately half as loud. It corresponds to an amplitude decrease of about 1/3.16 times in sound pressure and 1/10 times in power, creating a clear sense of sudden quietness, as if the volume has been sharply lowered.
-20dB
The sound diminishes to an almost inaudible level. It corresponds to a 1/10 reduction in sound pressure amplitude and a 1/100 reduction in power, resulting in a faint whisper-like presence within a noisy environment.
Decibel Unit (dBu)
dBu represents decibels relative to a reference of one microvolt, commonly used to express the intensity of voltage signals. Typically, -10dBu corresponds to a voltage of 0.775Vrms and is used to indicate line-level signals in audio equipment.
Decibels Full Scale (dBFS)
dBFS represents decibels relative to full scale and indicates the maximum signal level in digital audio. 0dBFS represents the maximum allowable signal level in a digital system, and values greater than this indicate clipping.
Decibels Volts (dBV)
dBV represents decibels relative to volts and is used to indicate the magnitude of voltage signals. Typically, 0dBV represents a voltage of 1Vrms and is used to express line-level signals in audio equipment.
Sound Pressure Level (SPL) in Decibels (dBSPL)
dBSPL represents decibels of Sound Pressure Level and is used to express the intensity or pressure level of sound. Measuring sound intensity in decibels is commonly utilized in areas such as environmental noise assessment, output of audio equipment, and hearing tests.
Decibel A, B, C Weighting (dBA, dBb, dBc)
dBA, dBb, and dBc represent weighting factors used to measure the intensity of sound in different frequency ranges. For instance, dBA ignores low frequencies and emphasizes mid-to-high frequencies when measuring noise, while dBB and dBC have different frequency weightings.
LUFS (Loudness Units Full Scale)
LUFS, short for Loudness Units Full Scale, is a standardized unit used to measure the volume level of music or audio. LUFS quantifies the average volume of audio and is primarily used in broadcasting, streaming services, and music production to regulate or compare the levels of music or audio sources. LUFS helps maintain consistent volume across various music platforms.
LKFS (Loudness, K-weighted, relative to Full Scale)
LKFS, short for Loudness, K-weighted, relative to Full Scale, is an abbreviation similar to LUFS and is used to measure and represent the average volume level of audio. LKFS helps quantify and compare the volume levels of music or audio sources, primarily used in broadcasting and media production.
LUFK (Loudness Units, K-weighted)
LUFK, which stands for Loudness Units, K-weighted, is a decibel unit closely related to LUFS and LKFS. It is used to measure and represent the volume level of music or audio, particularly important for complying with broadcasting and audio standards.
Decibels are widely used in various fields, and each type of decibel is selected and applied based on the signal or property to be measured in the respective field. These types of decibels play important roles in various applications such as audio engineering, medical devices, telecommunications, environmental noise measurement, and hearing tests.
