Usually when you have a smaller speaker, you sacrifice the low end, but earbuds seem to manage to deliver substantial bass nonetheless. I assume the proximity to the eardrum helps, but I don’t fully understand how.
In: 2000
Think of a how a big 12” subwoofer sounds in a normal sized room.
Now, think of your ear canal, air-sealed by an earbud, as a tiny, tiny version of that room.
There’s less air and less space for the air to move around in, therefore a much smaller speaker can deliver comparable, if not better sound directly to your eardrum.
It’s basically just a much more efficient delivery system.
Instead of trying to fill a big room up with sound so that your ears pick up some of it, you’re gettin the sound directly injected into your ears with almost no waste.
Your small speakers are probably not making the deepest sounds you hear, your brain is creating them.
The [overtone series](https://en.wikipedia.org/wiki/Harmonic_series_(music) (or harmonics, or partials) is a bunch or resonating notes that happen when any note is played, it’s a fact of physical acoustics in our air. You hit an A on a piano then by nature you also hear an A an octave above (double the frequency) and then a note a 5th above that (E) then a 4th above that (A, again, but higher). Etc.
(There is a lot of math and variables here, saxophones and oboes only play the odd harmonics due to conical bore, other instruments have their own unique harmonic characteristics. This is why organs are able to sound like different instruments, too, choosing different groups of pipes allows the organ to emulate the overtone series of different instruments. Anyway.)
But! If you play only an overtone series without that first, Fundamental, note, your brain will fill it in. Can’t be stopped. Owl brains have been shown to do the same thing, it’s a part of our biology.
So, the people who make little speakers know this and they take advantage of it! Those little speakers, like in your phone, are not playing the lowest tone. They play the overtone series above it and your brain generates the lowest tone from there. This allows deeper tones than should be physically possible from that driver. Goddamn witchcraft.
(edited for clarity, I hope)
A high-end 15” subwoofer in a normal residential room will shake the walls. That same subwoofer in a gymnasium would be wildly insufficient.
The space the driver is trying to fill matters, and your ear canal is tiny.
I know this is ELI5 so I’ll give it a shot but ELI10. Imagine you are visualizing sound waves. The high pitched sounds will have a lot of wave crests in the period of time where the low pitched, bass, sounds will have fewer (i.e. they have higher frequency and/or the wavelengths are shorter). In a sealed cavity like your ear, the waves have to match a frequency in your ear membranes to perceive sound. Further, because the length of the ear canal is so short it is less than one wavelength for bass sounds. Bass sounds are low frequencies from about 20 – 250 Hz. This translates, at the speed of sound to a wavelength of about 17-1.3 meters. So how then is this wave received? Because of its length a lot of it is heard through your bones!! That’s right bass sounds on ear buds can be transmitted through bone and is one reason they are perceived so well. There are actually headphones or buds designed to work specifically through bone (good for hearing impaired people). Studies have shown that the closer a sound generator is to the ear the more of the sound is conducted through the bone and much more is transmitted through the bone for bass than for higher frequency sounds.
Sound is based off of SPL (vibrations). The volume of the space inside your ear is tiny. Proportionally the driver is huge to that volume. You can read some about it in the IEC 60942 to learn more about sound level calibrators (drivers) or IEC 61672-1 which is about sound level meters. So the receiving end of it. You can pirate them if you want.
Source: Calibration technician that does light, sound, electronics, magnetics, and other crap.
Earbuds have to send out a lot less sound compared to speaker as they sorta seal your ear and are much closer so the inverse square law applies less
Most don’t actually deliver that deep bass. What they do is raise the mid range sound to emulate the bass. There are only select brands that do actually deliver true bass. Which I’m not 100% on how it actually is delivered. I do know most cheap ones definitely don’t.
When it comes to waves and how they propigate trough air, the inverse-square law applies
You need a big speaker to have the same effect having your ear multiple meters away versus having the speaker 1cm away from your eardrum.
If you would put your head at the speaker at the same volume you would probably hurt yourself.
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Keep in mind that your ear drum doesn’t move that much even with low frequencies, we are talking about under a millimeter.
For that, if you plugin your ear with a tight seal, you would only need about the same movement from a in ear speaker to have the same effect.
We could even have even smaller speakers if we could directly put one on your eardrum.
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Also there are “bone conducting earphones” out there where the “speaker” is even smaller because conducting sound trough solid things is better than with air.
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Which ear buds deliver true bass?
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