Ear switching hat

Introduction
Public summary: 

Sound cues can help us figure out where things are located in the environment - try confusing your brain with the Ear-Switching Hat!

This magical hat will confuse your senses!
Useful information
Kit List: 

One piece hat

Packing Away: 

Lives in small grey floating box.

Frequency of use: 
4
Explanation
Explanation: 

The hat switches sounds from the left hand side to the right ear and vice versa. This leads to a couple of cool effects and is great as a way of attracting people who would otherwise pass by without stopping.

What to do (1):

Put the hat on a child or other volunteer - if they are very small you might have to get them to hold the ear defenders on.
Fairly quickly get them to shut their eyes, then go to one side or another and ask them to 'point where it sounds like I am standing' (these words partially get around the effect of the cunning kid who catches on very quickly and consciously changes where they are pointing).

You have two main ways of telling which direction a sound is coming from, volume and time delay. Which one you use depends on the frequency of the sound. Below 80Hz there isn't really an effective method; between 80Hz and 800Hz humans use the phase difference between their ears to determine location; between 800Hz and 1600Hz we're again a little lost but above 1600Hz we start using volume to locate the source of the sound. What about telling the difference between in front, behind or above us? That's the shape of our ears and heads that make sounds slightly different if they come from a different one of those positions. It's not perfect though, and a new noise in front of us sometimes sounds like it's behind.

What to do (2):

Put the hat on a volunteer (as before). Instead of getting them to close their eyes, get them to look (with their eyes only) to one side (right for the sake of description, although this works the same reversed). Stand more two people one either side of the volunteer. The person on the volunteer's right (who they are looking at with their eyes whilst keeping their head pointing forwards) mouths a simple sentence (for example: "My name is ...". They do this when counted in by the person on the left, who speaks the same words. For maximum effect, choose people with different voices/accents/genders and hopefully the person on the right will sound like they are speaking with the person on the left's voice. Maybe practice with some other demonstrators beforehand.

More information:

The brain integrates a range stimuli from the environment to help ascertain one's relationship to these. Particularly important is the processing of auditory cues - hence the vast majority of animals employ a 'two detector', i.e. two ear, system to pick these up. By comparing the input from one ear with that on the other side, special centres in the brainstem figure out the 3D origin of a sound wave - at its most simple level by comparing the intensity (volume) of the input to each side and the delay from one side to the other, but also by the more complex changes in pitch (frequency) that occur due to a 'acoustic shadowing' effect (different frequencies are affected differently by passing through your head) that the head getting in the way of a sound wave has!

The importance of this is huge - as predators this may help us to hone in our prey, rustling in the undergrowth, or in the converse situation, helping us figure out how to avoid being someone's next meal! This is evident in how most predators typically have relatively small external ear parts compared with many more 'docile' creatures with very large external ears (pinnae) that in many cases (such as rabbits and hares) can even be directed (kids might then ask about elephants - their ears are large for a very different reason, for cooling, much as the 'sail' of some dinosaurs is speculated to be) to help them localise sounds better (and I can't begin to imagine how complex the neural network integrating ear position with auditory input must be.)

In theory, if someone wears the hat for long enough, processes of synaptic plasticity will take place in the brain re-mapping inputs so someone can adapt to respond to sound cues in the correct direction. But even in the short term people can get used to the switched inputs and respond appropriately, much like an experiment that involved volunteers wearing prism glasses that inverted their environment - they were asked to throw a basketball into a net, which initially was impossible for most, but over time, presumably through cerebellar motor learning they adapted to their new state and were able to function perfectly normally despite seeing everything upside down! (intriguingly, when the prism glasses were removed, although it still took them time to adapt back to 'normal' again, it took less time than it did to learn when they tried the glasses for the first time).

So in people who have reduced hearing on one side, it's often still possible for them to discriminate whether sounds are coming from one side or the other due to these plastic changes, although it may not be as accurate.

Hearing is even all the more clever when you take into account how the hair cells of the cochlea can 'tune in' to certain frequencies and desensitise to others. Insect hearing is rather different to the above but (I think!) a basic intensity compatator is still employed, together with other clever mechanisms to distinguish externally-produced sounds from internal ones via a mechanism of 'corollary discharge'.

Risk Assessment
Date risk assesment last checked: 
Sat, 27/01/2018
Risk assesment checked by: 
jaredjeya
Date risk assesment double checked: 
Sat, 27/01/2018
Risk assesment double-checked by: 
Matt Worssam
Risk Assessment: 
DESCRIPTION Hat that switches sound between ears
RISKS
  1. Risk of hearing damage
  2. Risk of disorientation and falling over, especially if they have closed their eyes
  3. Tubing may get caught on wearer
  4. Risk of transfer of hair infestation (e.g. headlice)
ACTION TO TAKE TO MINIMISE RISKS
  1. Warn children not to shout loudly into ears, and make sure you talk quietly into the ears
  2. Tell child to sit down if they feel disorientated/dizzy
  3. Make sure that the surrounding area is clear (especially of sharp objects) before letting the child close their eyes
  4. Warn child not to pull hat off quickly to avoid injury, especially with long hair
  5. Visually inspect hat between use.
ACTION TO TAKE IN EVENT OF INJURY Call first aider in event of injury
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Images
Publicity photo: 
Experiment photos: