I just can’t wrap my head around it. Is it just crazy brain things, a difference in number of waves, or some other thing? How is it possible that a speaker can replicate all sounds?
In: 24
The sounds you hear are never just a pure wave. If you were to record them, using a microphone, and look at the graph of pressure over time, you would never see a basic sine wave. Every real sound is a combination of many of those waves.
To visualize this easier, imagine it like one of those wave pools that have many pusher plates, like [this one](https://youtu.be/pir_muTzYM8). They can create the most basic kind of wave by just going back and forward at regular intervals, but they can also activate independently at different times and create different waves with different frequencies and different offsets that all mix together in the pool. Those are like the sounds around you, all mixing together in the air, which, when interacting with your ear, will come together as one singular, complex wave. As a sidenote, your eardrum works the same way as those pusher plates on the pool, just in reverse. The differences in pressure push the drum in and out, and your brain registers it.
There’s a mathematical operation called a Fourier transform that makes it possible to take in a complex wave and break it down into every single simple wave that made it. Your brain does the exact same thing, just unconsciously and extremely quickly. That way, it can separate all the sounds from everything around you and tell the dog barking apart from the fan going in the background.
The actual “sound signature” of each object exists because they, themselves, produce a complex wave instead of a simple one. They have a frequency and an amplitude (which we perceive as the pitch and the loudness respectively), but they have a distinct shape. That’s how a violin and a flute can be playing at the same pitch and the same volume but still sound completely different. [Here](https://www.researchgate.net/figure/Waveforms-of-different-instruments-at-a-particular-frequency_fig1_305333971) is a graph visualizing the difference for a couple instruments. A tuning fork is built specifically to get as close as possible to the pure sound, to a basic sine wave with the specific frequency it’s tuned to.
Just to clarify.
3000 MHz is 3 000 000 000 Hz. I don’t even think sound like that can exist. At least not in air.
Human hearing ranges from 20 to 20 000 Hz.
And to answer the question, sound is never really only at 1 specific frequency but is a variable and complicated wave.
Our brain is really good at taking complicated patterns and making them identifiable.
The human range of hearing is roughly 20 Hz – 20 kHz, so a 3000 MHz signal would not be detected at all. But in general, the inner ear contains many tiny sensory hair cells, each sensitive to a narrow range of frequencies. This allows the brain to split a signal into its frequency components. How exactly the brain processes this data into something we consciously perceive as noises or speech is not fully understood. We have some idea of what the function of certain brain regions is, but at the lowest level the brain consists of incredibly complex neural networks, which are currently practically impossible to fully analyze.
In short, overtones. It’s not just one sound at one pitch, but a blend of many higher pitches.
A pure tone is a sine wave. That’s generated with an electronic device. It’s the top wave in this [graph](https://en.wikipedia.org/wiki/Square_wave#/media/File:Waveforms.svg). You can create waves of different shapes by adding a bunch of different sine waves on top of each other.
On that graph, the y-axis is pressure and the x is distance (or time since the waves travel). By taking a bunch of different sine waves with a wavelength of 1/2, 1/3, 1/4, (and so on) of the first, they can be added together to get a wave that’s shaped differently but has the same frequency. Here’s a [gif](https://en.wikipedia.org/wiki/Square_wave#/media/File:Fourier_series_for_square_wave.gif) of a square wave being made by adding together a bunch of sine waves.
By precisely choosing the amplitudes and phases of each wave, waves of any shape can be generated. Waves with different shapes at the same frequency will sound different even though the pitch is sounds the same.
Your ears have a membrane that vibrates that gets read as an electrical signal your brain interprets cause your brain runs on electrical impulses and chemical packets fired between your neurons.
The electricity helps move the chemical packets
A specific frequency wave is just a tone. When we hear a voice, car, or alarm, it’s tons of waves all at different frequencies, adding together at the same time that turns it into a sound that we can distinguish.
In music, A above middle C is 440Hz. If you had any instrument playing that note, it would have a fundamental frequency of 440Hz, but it would still sound different than a pure 440Hz sine wave (tone). That’s because the instrument has so many different places the wave can bounce around clash with itself, creating a bunch of harmonic frequencies that when they add together, we can tell if it’s a piano, or a violin, or a trumpet making the noise.
[Here is a tone generator](https://www.szynalski.com/tone-generator/) you can play around with different frequencies, and you can see how a sine wave, square wave, triangle wave, and sawtooth wave all sound different despite being the same frequencies. It won’t let you add them together, but it’s a good basis for how sounds are different from each other, even if they are the same frequencies.
If you’ve ever heard a powerline arc, it’s the same sound as a 60Hz (or 50Hz depending on where you live) square wave.
Im not sure this is what you are looking for, but basically, your brain makes it up. At some point in evolution, there was an advantage gained if your brain created a different sensation to differentiate two different vibrations in air. I dont think scientists know how your brain does this, but we do know how the data gets to the brain: there are structures in your ear (a hammer and a drum if your are five 🙂 that cause different electrical impulses to travel in a nerve when different vibrations are experienced.
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