Ears! How can we know a where a sound is coming from? Sound localisation.
Left And Right
It may be common sense that determining whether the source of a noise is located to the left or right of us has something to do with the fact the noise would appear louder in the ear closest to its origin.
We might even go as far as to deduct that a sound will be heard by the ear closest to its source slightly before it is picked up in the other ear, thus making it possible to know a sound is coming from the left or right.
But the ears don't merely distinguish if a noise is appearing from the left or right. Much like having two eyes will help us construct a three dimensional visual of the world, having two ears helps us construct a three dimensional soundscape of the world around us.
We can differentiate the distance between the loud hum of a faulty street lamp over the road and the quiet buzz of a bloodthirsty mosquito perched on our ear lobe. We can discern if a noise is appearing from in front, behind, above or below.
Our basic explanation of how the ears work are that sound waves enter the ear and cause the ear drum to vibrate, tiny bones attached to the ear drum send the vibration into a snail shell shaped thing in the inner ear which is full of fluid and tiny hairs, the hairs respond to the movement of the fluid which sends a signal to the brain that is interpreted as noise.
But what cues are the brain picking up on in order to translate the wave information into determining location?
Interaural time difference
If a sound comes from the left it will reach the left ear under a millisecond before the right ear, the brain is able to recognise this slight time difference.
Interaural level difference
Low frequency bass sounds have an omnidirectional tendency and wrap around objects meaning the sound level can be the same in the left and right ear despite whether the noise is coming from the left or right.
High frequency sounds are much more directional so the sound level is picked up as loudest in the ear closest to the source of the noise as the head obscures these frequencies casting an acoustic shadow over the ear furthest from the source.
Head-related transfer function
Now this is where the brain gets really clever and is able to determine quite accurately the direction of a sound source be it from in front, behind, above or below.
The outer ear (the pinna) and the head affect the levels of different frequencies in such a way that the brain can decipher this as the direction of the sound.
In simple terms it is like having a stereo with a bass, middle and treble equalizer. Turning the treble down on a piece of music would make it sound distinctly different, and so it would cutting the bass or middle.
The pinna and head make for subtle cuts or gains in frequencies that are unique to whether the noise is appearing directly above, behind or below, or from any given angle in the audio field.
It is thought that the the brain may even take into account the sound reflected into the ear off of the upper body as a further cue in locating sound.
So how do we detect the distance of a sound?
There is a lot of speculation about how we may detect the distance of a sound source and has much to do with how the reflections of distant sounds differ from near sounds in the time the reflections take to reach the ear, as well as atmospheric distortions to the sound wave or sound quality as it travels through space.
Personally I think it's because of magic.
You have a minor misspelling in the following sentence:
It should be piece instead of peice.I do not appreciate that being pointed out in my comments.
It is very good and informative post. I do like it...O
I feel that distance of sound certainly includes reflections, but more than that we are using felt sense of resonances within the matter in our vicinity - plus the overall acoustic signature changes caused when sounds vibrate in the air over time and other issues relative to the shape of the earth and environment in general..
It would be interesting to find out how sounds are experienced elsewhere in the universe!
sounds in the distance kind of appear to take up more space don't they? There was an experiment where they played the same noise at different distances but that reached the ear at the exact same amplitude, the subjects still successfully determined which was closer and further so it must be environmental factors, and perhaps you are right that there may actually be senses other than hearing at play, the various parts of our body all have resonant frequencies.. I wonder how much of a role this plays in how we perceive hearing. I met a deaf dancer once who was able to dance to music because he literally felt it.
Oh yes, feelings are a large part of this. Sounds are clearly vibrations and we are vibrational beings first and foremost. There are examples of people seeing perfectly well while wearing major blindfolds too - but that is beyond feelings and into the realms of 'extra sensory perception'.. :)
I have been able to lean my whole body against the waves coming from a massive bass setup in a nightclub (standing in a doorway) - the bass literally held me up.. So it is clear that our whole body is capable of feeling sounds and of playing a role in sound perception.
I think it will help to examine how dolphins use their 'sonar' to model their reality if we are to understand how our own mind processes sound in 3D.
interesting, that must be why bats used high pitched sounds for echolocation
Yeah they wouldn't be able to locate food using bass but they might be able to start some sort of funk acapella group and busk for food. Ultrasonic noise is used in ultrasound scans too.
there are some blind humans who navigate by echolocation.
Fascinating our body and what it can do. We know nothing really and definitely don't use it to the full capabilities. Thanks for sharing very educational. I also feel we pick up energies too in much the same way so can sense say a person approaching from out left through out energy field. Would you agree with this also ?
One of my first steemit posts was about unified field theory, basically it was once thought that electricity and magnetism were two separate forces until they discovered elecomagnetism which proved they were both in the the same field of energy, Einstein thought if gravity could be shown to be in the same field as electricity and magnetism then it would prove one absolute energy from which everything is manifest. Tesla had a firm belief or understanding of the oneness of everything and its electromagnetic nature. Quantum physics has gone a long way towards proving the absolute. So yeah basically I think/feel all of our senses are a concentrated magnetic kind of energy manifest in an absolute field, it's a subject we could get quite deep into. There is a book by a guy called Greg Goode called the direct path which gives interesting pointers at how we actually experience the world, worth a read.
Very interesting stuff. I'll ad the book to my massive books list, need to got off Steem and reading 💯🐒
This is extremely well thought out-- technical and informative but also written in a very accessible way. My husband, who is an AV tech and Audio Engineer/Designer, would totally appreciate this. In fact, I think I am going to send it to him. :D Thanks for sharing, you now have a new follower. I look forward to seeing more of your posts!