I am a professional musician and a professor of music technology who studies acoustics. My work investigates the intersection between the scientific, artistic and subjective human elements of sound. Choosing the right headphones involves considering all three of those aspects, so what makes for a truly good pair?
In physics, sound is made of air vibrations consisting of a series of high and low pressure zones. These are the cycles of a sound wave.
Counting the number of cycles that occur per second determines the frequency, or pitch, of the sound. Higher frequencies mean higher pitches. Scientists describe frequencies in hertz, so a 500 Hz sound goes through 500 complete cycles of low pressure and high pressure per second.
When sound enters your ear, your eardrum translates the air vibrations into mechanical vibrations of the tiny middle ear bones. These mechanical vibrations become fluid vibrations in your inner ear. Sensitive nerves then turn those vibrations into electrical signals that your brain interprets as sound.
Although people can hear a range of pitches roughly from 20 Hz to 20,000 Hz, human hearing does not respond equally well at all frequencies.
For example, if a low frequency rumble and a higher pitched bird have the same loudness, you would actually perceive the rumble to be quieter than the bird. Generally speaking, the human ear is more sensitive to middle frequencies than low or high pitches. Researchers think this may be due to evolutionary factors.
Electromagnetism states that when a wire is wrapped around a magnet and the current within the wire changes, the magnetic field around the wire changes proportionally. When the electrical signal of a song or podcast pulses through the wires in a set of headphones, it changes the current and moves the magnet. The magnet then moves the diaphragm in and out—kind of like a plunger—pushing and compressing air, creating pulses of high pressure and low pressure. This is the music that you hear.
Ideally, a speaker would convert the electrical signals of the input perfectly into sound representations. However, the real physical world has limitations. Things like the size and material of the magnet and diaphragm all prevent a speaker from perfectly matching its output to its input. This leads to distortion and some frequencies being louder or softer than the original.
While no headphone can perfectly recreate the signal, there are infinite different ways to choose to distort that signal. The reason two equally expensive headphones can sound or feel different is that they distort things in different ways. When engineers build new headphones, they have to not only consider how human hearing distorts sound, but also the physical limitations of any speaker.
Source : https://www.popsci.com/technology/choose-right-headphones-sound/