Passive Echolocation Signals

Passive signaling during echolocation involves listening to the ambient noises in the room and interpreting them. It has it's pros, such as not being intrusive or noticeable, but it is not the best method for accurate echolocation. These sounds can be:

• People talking
• A running fan
  
• Footsteps
• Clothes rubbing against each other
• Hands rubbing together
• Breathing
• or other omni-directional sound sources.

One of the downfalls of these sounds is the fact that their source is undefined, and therefore any sound that is reflected to the listener has the potential to be bouncing from any direction and can not easily be used to identify the shape of objects.

These sounds can however be used to make broad observations such as the size of a room or proximity to a flat wall. Other estimations may be possible depending on the actual content, level and clarity of the sound and any other distracting sounds that also exist, noticeable or unnoticeable.

Echolocation in Terms of "Reverb"

Image by Northeast Indiana via FlickrLet's look for a second, at echolocation as it would be viewed by a musician. Every different room, every environment, indoor, outdoor or otherwise has it's own acoustical properties. These would be known to musicians as that room's reverberant properties, or it's "reverb". Certain rooms are said to have a certain type of reverb. Rooms with hard flat parallel walls generally have what is considered to be "a lot" of reverb, where rooms with softer (more absorbant) walls that are oddly mishapen are said to have less reverb, meaning that the sound is not as likely to bounce around as much. A highly reverberant room is labelled such because the sound waves are likely to bounce off of the walls, sometimes several times before making their way to the listener. This gives the effect that one short tone is stretched out over a longer period of time. Essentially, the reverb is made up of many very quick echoes from nearby structures.

You have undoubtedly experienced and are familiar with certain reverb characteristics. For example, if you are in a quiet environment and you close your eyes and snap your fingers, you will immediately be able to tell if you are in a bathroom, car or auditorium. If you thought about it a little longer you could probably guess if the floor was carpeted and what the walls were made of.

Since the exact shape of any room give it it's reverb, this is essentially the same thing as echolocation. Save for one small detail, movement of the source and reciever (sound source and your ears). A room can have reverberant qualities and you may be able to make generic assumptions about the make-up of the room by listening to a sound, but without moving the source and reciever you would be hard pressed to tell the shape of the room or identify any objects in it.

Once we move, we gain another dimension of information. The "echoes" which are making up the reverb we are listening to as we click to echolocate, are changing direction as we move our head. It is not one click that gives us the information we require, but rather the difference between one click and the next which tells us how objects are moving with respect to us, and therefore how we are moving with respect to these objects.

If you have watched people echolocate, you will notice that they move their heads from side to side, tilt their ears and walk around objects in order to distinguish what they are. They are taking the information differential between clicks and piecing it together like pieces of a puzzle. It may take several clicks before someone is comfortable in their surroundings or can identify an object. I would think it to be nearly impossible to gather much environmental information with just one click no matter how good versed you are in echolocation.

Beginner Lesson #2 - The Basics of Echolocation - How to Know What to Listen For

Image via WikipediaIf you've never tried to echolocate before and don't really know what it is, then read this article, it will give you an idea of what to listen for.

One of the first times I noticed the effects of echolocation, I was sitting at my desk at work, and listening to the radio. The speakers were biased to one side of my head, and I raised a hand up on the opposite side of my head - maybe one foot away - and found that the sound reflected off my hand and into the ear that was getting less music. Try this, and now move your hand around a listen for the sound reflections. If it's not obvious enough with just your hand, try a folder or binder (something larger, flatter, and more rigid will be a better reflector). The image above illustrates why flatter surfaces make better reflectors. Sound reflects off of objects similar to the way light does.

Now try twisting your hand or binder back and forth, but keeping it in one place so that you're reflecting the sound away from your ear, and then directly at your ear, and then away in the other direction. It should appear as if the sound source is passing by, while really, it is just the shape of the reflecting object creating different effects.

The effects you will hear from this exercise are quite a bit more pronounced than the effects you will see when you start using clicking to echolocate, but this should give you a good idea of what kind of effects can be observed when sound reflects directly off of a small object.

Echolocating Through a Doorway

Image via Wikipedia

To get a feel for echolocating you can try this quick exercise in an inside doorway.

1. Stand 3-4 feet in front of a doorway. If possible the door should be positioned in a flat wall and it should be fairly clear of obstructions on either side. Make sure there are not too many distracting noises surrounding you, it’s certainly easier if it’s a very quiet environment. Oh yeah, it’s also important that the doorway does not have a threshold, this will be a dead give-away later on.
2. Close your eyes and listen. Take notice of any ambient noise around you. Notice how these ambient noises change as you turn your head. Address the doorway and make the clicking noise of your choosing. Turn your head back and forth to click in the direction of both sides of the doorway. Step forward toward the doorway and observe the changes.
3. Finding the door. Step all the way through the door and notice the changes in sounds from one room to the next. Try to hear when you are exactly inside the door jam. Try to hear if you are closer to one side than the other, remember to keep turning your head. Focus on one ear at a time, what are the differences? If you think you’ve made it, open your eyes or grab onto the door jam to see how you’ve done. If you’d like you could try turning 90 degrees and approaching one of the sides of the door jam and see how close you can get your nose to it without touching it. While clicking, make your estimate before you verify your success.

Intermediate Echolocation Lesson #1 - Walking a Predetermined Path

I was visiting a friend down the road last night, and on my way home it was fairly dark and there were not a lot of people roaming around my little suburban-type town, so I was able to get in some good echolocation practice. My trip was about 1/2 mile and it is a fairly straight shot on a somewhat even sidewalk. I am still very much a beginner at this so if you already echolocate, this will probably not be news to you, I can only offer my observations of myself as I'm learning.

This was my method that seemed to be fairly fruitful:

1. Sighting your target. With your eyes open, look ahead, down the path that you are to travel. I find that somewhere between 30 and 60 feet is a good starting distance. Pick a distance that is long enough so that you will not be able to count your footsteps, but short enough that you will not get discouraged or lose track. Pick a landmark at the end of the path; a telephone pole or bush that you can end at. Familiarize yourself with the lay of the land so that you will have a starting point and some familiarity. Notice changes in terrain, bushes, parked cars, telephone poles, fire hydrants, etc. If you are blind then you'll most likely be attempting to navigate a path that you have previously used a cane for, and are familiar with the obstacles that you must avoid.
2. Setting your course. Once you know approximately where you're trying to get and what obstacles you need to avoid, it's time to set you course. Which side of the tree will you walk on? Will the fire hydrant by to your left or your right? Will you need to adjust your direction to navigate around obstacles? By doing this you will be able to break up your echolocation journey into smaller segments. (IE, after the firehydrant, vear right to avoid the overhanging bush.
3. Closing your eyes. Close your eyes. If you are blind this mean stowing your cane. You will probably be tempted to peek... it is natural, but don't, it kinda defeats the purpose..
4. Echolocating. Now to begin the echolocation journey. The first few steps you will be expecting. The immediate terrain and obstacles will be in your short term memory and you will easily navigate them without clicking. But click anyway so that you can hear and get familiar with the echoes. As you approach your first large object, maybe a car, tree or telephone pole, be aware that it is there. Listen for it and concentrate on the echoes. Obviously, the point here is not to touch anything that would give away the path, but if you are nervous about smacking your face into anything you can keep your hands up. I would suggest keeping them low and out of the path of your clicks, however.Objects that are nearer to your starting point will be easier to pinpoint. Click in the direction that you are expecting to find an object. Once you have reached a landmark, acknowledge it, try to judge it's distance, and then visualize your path with relation to it. What is the next landmark? The car on the left? Focus on the path and continue down it with a strong concentration and expectation of hearing the reverberation off the car. Once you get to it, acknowledge it. Notice the differences between the car and the telephone pole. The telephone pole, since it is round will sound the same from any direction. The car will change its reflective properties as your angle to it changes. I find that cars and metallic objects also reflect higher frequencies due to their less absorbent characteristics.
5. Reaching your goal. Once you have navigated yourself through you predetermined path, you should be at your end landmark. Be sure to stop when you have gotten to the landmark and acknowledge it. If possible, walk around the object still echolocating and clicking towards it. Remember not to touch it! Are you sure this is the correct object? Or is that thing you think is a telephone pole actually a bush? How far away from it are you?
6. Open your eyes. Take out your cane. Confirm the object that you've approached. Is there even anything there? How close did you come? Keep clicking for a little bit to understand what you are hearing. Where you hearing another echo from a nearby tree that threw you off? Did you judge the distance accurately?

Now wasn't that fun? As I'm typing it, it got a bit more involved, and I will certainly be typing up more exercises that might be easier, and as I progress, getting a little harder. Good luck with this one and don't get discouraged if you're not getting it. Just try objects that are a little closer or larger.

The Profundity of Echolocation and the Human Race

Image via Wikipedia
Echolocation is a physical ability that we possess and has been proven by many blind people. Its primary function is currently with the blind population, and while the blind are said to have more acute hearing, it has been tested (even amongst the best echolocators) to be no "better" than the average person. They have simply been given the opportunity to put more focus on it and thus have become more in tune with its subtleties.

Hundreds of thousands of years of human development are to be attributed to the fact that we use tools, brains, and all of the physical abilities at our disposal. Echolocation is an ability that has gone unacknowledged for many thousands of these years. Certainly there have been people to use it, most likely blind, (the case of James Holman stands out as notable amongst many blind people who claimed to be able to see objects via "pressure" on their face, or "facial pressure") but it has not been brought to the attention of the mainstream public until very recently.

Imagine that the human race had never realized that it was possible to hurtle one's body through the air, curl it up into a ball, flip around and land on one's feet. The first time someone successfully landed a front tuck was a revolutionary turning point in one small area of human development. Gymnastics is an incredible ability that is not necessarily feasible for everyone, but the human race has worked hard to develop it into a sport and a form of entertainment. People teach it and practice it because it is challenging and enjoyable.

This is much like echolocation. If your parents had told you that you could hear the sound reflected off of objects, and told you "Listen to where the tree is" just like they told you "Look at what color the ball is" then you probably would have grown up with at least an acknowledgment of the existence of this ability. It is human nature for people to explore their own abilities and therefore you probably would have practiced or at least noticed this sense in your development. Now, what if people had been developing this ability for the past 10,000 years, just like the abilities of speech, walking or running. Imagine where we would be. The world of darkness and blindness would be so much less foreign to us and there would be many opportunities and abilities which inherently implement echolocation that would easily become apparent should we refine this ability.

As Eric Schwitzgebel stated in his blog Echolocation and Knowledge:

...most of us, even if not wrong in quite that way, are strikingly ignorant about this aspect of our stream of experience.

We have so much room for development in the area of echolocation, and so much to learn. I'm glad that we have not reached the final plateau in learning about ourselves (although I know that would be an outright impossibility).

Working on the best Click for Echolocating

The sound emitted during echolocation is critical since it is the direct properties of the reverberations of that sound that you'll be analyzing. This means:

1. It's got to be a sound you are familiar with. You know the sound of you front door and you know the sound of a soda or beer can being cracked open. Sounds like these are powerful in that they instinctively trigger thoughts and emotions prior to you actively conceptualizing their source. The sound you use for echolocating should be similar to this so that you are familiar enough with it to recognize the very subtle variations that are necessary for echolocation.
2. It's got to be consistent. Whatever it is try not to change it up to often unless you experimenting. One sound may return different reverberant characteristics than another in the same environment.
3. You've got to be able to hear it. It doesn't make a lot of sense to make a sound that will be difficult to hear, which implies that the sound wave must have enough energy to return to your ear, and still be recognizable. Higher frequencies have a higher energy than lower frequencies and therefore will return better. They will also give you better resolution since the wavlength is shorter.

Here are a few of the different tones I've been experimenting with:

1. Car engine. This is used when driving with the passenger's side window open and echolocating passing objects. Read echolocating while driving in the car, for more, but you've got a great tone for a lot of reasons:
   
   • There are many different frequencies present.
   • It is consistent.
   • It is loud. I have been able to echolocate and determine the shape and material of objects up to about 50 feet away from the car.
   • It is not directly heard inside the car. Meaning most of the sound is outside the car and can be reflected inward making the reflected sound the dominant one as opposed to the source.
2. Footsteps. These are okay to use since they are generally distinct and high frequency, but I find that they are very inconsistent depending on the terrain and what kind of shoes you are wearing.
3. Scuffing of pant legs. Fairly consistent, but usually just not loud enough.
4. "Cluk" - The sound of the tongue smacking the bottom of the mouth as if to make a "clop" or "pop" sound. As far as I can tell this is what most practicing blind people do including Ben Underwood. It gives a nice quick defined tone that is fairly high pitched. And since the mouth is closer to the ears than say, the feet, the reverb characteristics, I would think, are more accurate.
5. "Kik" - This is a sound made on the sides of the tongue as if you were guiding a horse. It is made by sealing the tongue against the roof of the mouth and creating a negative pressure inside your mouth and then releasing your tongue's seal. It will result in a "kik". I've taken a liking to this one for a few reasons:
   
   • It's even higher pitched than the "cluk".
   • It's easier for me to make, therefore I can make it louder.
   • It emanates from the sides of the mouth rather than the front thus reflecting more of the tone directly back into the ears.

So I'm going to keep using the "Kik" method and we'll see how that goes. Another thing I wanted to try was snapping with my fingers somewhere under my chin. I will try this and report back if it is any good. The reason I say under the chin, is so that the sound source is close to my ears, but the direct signal is somewhat blocked by the underside of my face leaving me with a better perception of the sound as reflected back.