Why Learn Echolocation as a Sighted Person?

The benefits of acquiring the skill of echolocation as a blind person have obvious impact to the way you interact with your surroundings on a daily basis.  Any insight that echolocation can offer adds incremental information directly to your perception.

As a sighted person, to train echolocation, you must close your eyes.  This is inherently reducing your amount of perception and starting at a level that you are not comfortable with and you may have very low confidence navigating in the dark.  So why would you want to learn??

I asked sighted people in a survey why they wanted to learn echolocation below are some of the common responses:

• To continue my life normally if I ever were to lose my sight.
• To continually and aggressively exercise my brain.
• It's a fascinating subject and an interesting skill to learn.
• I'd like to be able to navigate in the dark better.
• To aid in understanding of visually impaired people whom I work with.
• And many other good reasons along these lines.

Personally, I can come up with a thousand ways echolocation can benefit sighted people... okay maybe not thousands... but at least a few.

In today's world people are becoming more and more open to exploring new methods of learning and growing as a society.  This blog is a good example of that..  I can put this very obscure information out there on the web and there are hundreds even thousands of people who read these articles and respond to them with their feedback and stories about how they are learning echolocation.  It's wonderful to see so many people opening their minds to new possibilities and seeking out new challenges.

Working the brain muscle is always a good thing to do.  Things like learning new languages, learning a musical instrument, learning to cook or learning how to juggle or otherwise improve your coordination is great medicine for the brain.  Notice how each of these examples starts with the word "learning"?  See a pattern?  Learning echolocation is, of course, great brain exercise, but the fact that echolocation is likely to be a completely foreign concept requires entirely new channels to be opened in the mind.

Eventually, not this decade and probably not this century, but eventually, I'm certain that echolocation will become a mainstream mode of perception for all humans.  It will be taught from childhood and will have several applications in daily life.  It can help us become a better race and a better society.  This is the natural way of evolution and new skills like this have been added to the human skillset for thousands of years.  We will always continue to grow and develop as a species.  We can be a little ahead of the curve and essentially see into the future by recognizing these skills now and being part of the driver that helps them propagate to future generations.

Everyday we should challenge ourselves.  This is the only way to improve ourselves.  Each day that passes without overcoming adversity or learning something new or standing up to face a new challenge is a day wasted.  A phrase that we would recite in Portuguese at the beginning of a martial arts class I took was: "Each day that passes, I am improving everything that I do."  Every day I want to become a better person and challenge myself in ways that I did not challenge myself the day before.  Echolocation is a great new horizon on which I find many challenges, and it is for that reason that I find it so alluring.

Matthias' Journey into the World of Echolocation

Through one of my acquaintances at World Access for the Blind, I recently found this new blog from the mother of a blind child named Matthias.  Matthias is 4 years old and completely blind and he has recently been introduced to echolocation by taking a 4-day workshop with Justin from World Access.  This article on the blog explains the experience of having Justin to the house and how receptive Matthias was to the training..  It's quite humorous and well written.  I would suggest that everyone interested in echolocation training for children subscribe to this blog because there is sure to be more interesting insights coming from it as Matthias improves his skill.

His mother (after reading several posts I still can't figure out her name; it might just be "I") also has a YouTube channel with great videos of Matthias learning echolocation by playing simple games.  One of those videos is here:


I love seeing young kids like Matthias learn echolocation (whether they resist learning at first or not) because I'm sure it will change his life for the better.  Per the blog post here entitled "Echolocation... because our son is smarter than a bat", Matthias has already begun to increase his walking speed which was troubling him, so that he can better keep up with his friends and play games.

Way to go Matthias!  Keep up the good work!

Frequency Absorption Characteristics of a Variety of Materials

In order to understand a topic fully, it's important to deviate sometimes and uncover bits of data that are not necessarily contributing toward our physical training or implementation, but instead, add to our overall understanding of a subject.  Whether or not you actively utilize this information during your echolocation practice is not important, however it is important to understand and acknowledge it.

In this case, I would like to take a look at how different materials absorb different frequencies.  This will help you to understand how softer items, like upholstered furniture, might differ from doors and how doors differ from concrete.  The numbers listed in this chart are the "absorption coefficients" of these materials.  

To give you an idea of how it works, carpet, the first item on the list has an absorption coefficient of 0.01 for 125Hz frequencies.  That means that it will only absorb 1% of a tone at a frequency of 125Hz.  It will absorb 2% of a 250Hz tone, 6% of a 500Hz tone, 15% of a 1kHz tone, 25% of a 2kHz tone and 45% of a 4kHz tone.  

It becomes easy to tell that some materials absorb a good percentage of some signals, but reflect a good percentage of other signals.  Remember that any percentage of the signal that is not absorbed is reflected.

The reason we start learning echolocation using hard flat objects is because of the fact that, as you see below, things like glass only absorb 2-3% of most frequencies and are therefore very reflective, or responsive.  As opposed to things like upholstery and people which absorb at least 25% of most frequencies, and up to half of some of the higher frequencies.

Material 125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz carpet 0.01 0.02 0.06 0.15 0.25 0.45 Concrete (unpainted, rough finish) 0.01 0.02 0.04 0.06 0.08 0.1 Concrete (sealed or painted) 0.01 0.01 0.02 0.02 0.02 0.02 Marble or glazed tile 0.01 0.01 0.01 0.01 0.02 0.02 Vinyl tile or linoleum on concrete 0.02 0.03 0.03 0.03 0.03 0.02 Benches (wooden, empty) 0.1 0.09 0.08 0.08 0.08 0.08 Benches (wooden, fully occupied) 0.5 0.56 0.66 0.76 0.8 0.76 Theater seats (wood, empty) 0.03 0.04 0.05 0.07 0.08 0.08 Theater seats (wood, fully occupied) 0.5 0.3 0.4 0.76 0.8 0.76 Seats (fabric-upholsterd, empty) 0.49 0.66 0.8 0.88 0.82 0.7 Seats (fabric-upholsterd, fully occupied) 0.6 0.74 0.88 0.96 0.93 0.85 Brick (natural) 0.03 0.03 0.03 0.04 0.05 0.07 Brick (painted) 0.01 0.01 0.02 0.02 0.02 0.03 Concrete block (coarse) 0.36 0.44 0.31 0.29 0.39 0.25 Concrete block (painted) 0.1 0.05 0.06 0.07 0.09 0.08 Concrete (poured, rough finish, unpainted) 0.01 0.02 0.04 0.06 0.08 0.1 Doors (solid wood panels) 0.1 0.07 0.05 0.04 0.04 0.04 Glass (1/4" plate, large pane) 0.18 0.06 0.04 0.03 0.02 0.02 Glass (small pane) 0.04 0.04 0.03 0.03 0.02 0.02 Drapery (10 oz/yd2, 340 g/m2, flat against wall) 0.04 0.05 0.11 0.18 0.3 0.35 Drapery (18 oz/yd2, 612 g/m2, pleated 50%) 0.14 0.35 0.53 0.75 0.7 0.6 Performated metal (13% open, over 50mm(2") fiberglass) 0.25 0.64 0.99 0.97 0.88 0.92 Wood tongue-and-groove roof decking 0.24 0.19 0.14 0.08 0.13 0.1 People-adults 0.25 0.35 0.42 0.46 0.5 0.5 People-high school students 0.22 0.3 0.38 0.42 0.45 0.45 People-elementary students 0.18 0.23 0.28 0.32 0.35 0.35 Ventilating grilles 0.3 0.4 0.5 0.5 0.5 0.4 Water or ice surface 0.008 0.008 0.013 0.015 0.02 0.025

Source: http://www.sae.edu/reference_material/pages/Coefficient%20Chart.htm

Why a 3kHz Frequency Tone is Optimal for Echolocation

Below is a representation of the human hearing threshold which gives us a good idea as to why a 3 kilohertz (kHz) beacon signal is a good signal to use for echolocation.

This chart is plotting the intensity in decibels that is audible by the human ear at different frequencies along the audible spectrum of sound.  Additionally, the different lines represent different signal "loudness levels".  At lower frequencies, and lower loudness levels it becomes increasingly difficult to differentiate between tones. The lower tones, near 20 Hertz are only audible once they reach approximately 75 decibels (dB), which means that a low tone needs to be far more powerful to be perceived.  

There is a consistent dip around 3kHz where it is indicated that softer sounds are perceived just as well as other frequency tones of the same loudness.  As signals get higher in frequency, it is required again that they be of greater loudness in order to be perceived at the same level.

This has to do with the construction of the human ear canal.  A 3kHz frequency resonates nicely in a 2.4cm tube at body temperature, which is the average size of an ear canal.

Source:  http://hyperphysics.phy-astr.gsu.edu/hbase/sound/eqloud.html#c1

We have to remember however, that a single frequency tone is not entirely optimal due to other circumstances.  For instance, a 3kHz tone may be completely absorbed by an object.  Fiberglass boards appear to absorb these frequencies very efficiently, as well as upholstered benches according to this absorption coefficient chart.  For this reason, it is important to choose a signal that consists of a broad spectrum of frequencies.