A song played through the same equipment can reveal more details when the volume is increased. The quality of the recording and the playback system both influence how well audio details are reproduced. However, does louder always mean more detailed? This isn’t just about the playback capability of the equipment—it also depends on the human ear’s sensitivity.
To understand this better, let’s look at an important experiment in the history of sound perception. Known as the Equal-loudness Contour, this experiment demonstrated how our ears perceive different frequencies at varying volumes. In 1933, Harvey Fletcher and W.A. Munson from Bell Labs conducted this pioneering study, which has since been validated by numerous other researchers. In 2003, the International Organization for Standardization (ISO) released the ISO 226:2003 standard, based on these findings.
Below is a standard representation of the ISO 226:2003 equal-loudness contour.
Figure 1
Figure 2
Figure 1 shows the sound pressure level (SPL) on the vertical axis and frequency on the horizontal axis. The red lines represent the Phon value curve, with numbers indicating the loudness in Phons. Figure 2 reverses the vertical axis.
As shown in Figure 1, a 1 kHz tone at 20 dBSPL has a loudness of 20 Phons. For a 100 Hz tone to have the same perceived loudness, it needs to reach 50 dBSPL [3].
From these figures, we can draw several conclusions:
- Human ears are most sensitive to mid-range frequencies (around 1 kHz).
- Perception of low and high frequencies is heavily influenced by sound pressure levels.
- As volume increases, the perception of frequency becomes more linear, meaning that lower and higher frequencies become easier to detect.
In music, low frequencies contribute to a sense of power and depth, while high frequencies add brightness, clarity, and airiness. Therefore, increasing the volume can enhance the overall detail and richness of the sound.
Based on the above, under the same equipment, playing music louder can indeed make details more apparent to the listener.
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