Humans are Cleverly Stupid Beings

Quick note to put things in perspective:  If the whole of the electromagnetic spectrum were positioned on a tape measure and it was stretched to 2,000 miles, the amount of visible light that humans see is less than one inch.  So, on a logarithmic scale of frequency, visible light is 2.3% of the whole electromagnetic spectrum, while on a linear scale it is 0.0035%. The human eye see less than 100th% of the universe.The perception of loudness relates roughly to the sound power to an exponent of 1/3. For example, if you increase the sound power by a factor of ten, listeners will report that the loudness has increased by a factor of about two (101/3 ≈ 2). This is a major problem for eliminating undesirable environmental sounds, for instance, the beefed-up stereo in the next door apartment. Suppose you diligently cover 99% of your wall with a perfect soundproof material, missing only 1% of the surface area due to doors, corners, vents, etc. Even though the sound power has been reduced to only 1% of its former value, the perceived loudness has only dropped to about 0.011/3 ≈ 0.2, or 20%.

The range of human hearing is generally considered to be 20 Hz to 20 kHz, but it is far more sensitive to sounds between 1 kHz and 4 kHz. For example, listeners can detect sounds as low as 0 dB SPL at 3 kHz, but require 40 dB SPL at 100 hertz (an amplitude increase of 100). Listeners can tell that two tones are different if their frequencies differ by more than about 0.3% at 3 kHz. This increases to 3% at 100 hertz. For comparison, adjacent keys on a piano differ by about 6% in frequency.