Echo Location: Listening to Objects and the Environment

A common misconception is that those of us with a lack of vision, or no useful vision at all, are born with our other senses heightened. This isn’t in fact true; instead, we’ve had to work hard to refine the senses we do have (hearing, smell, touch and taste) to make as much use of them as possible. Naturally one of the key senses used by a blind person is auditory. Like you, we use our hearing to communicate with others, enjoy entertainment (music, film, TV etc) and to hear the sounds of the world around us. We however rely on our hearing as a means to stay safe, to navigate our surroundings, and, primarily in combination with our sense of touch, to explore everything that you would using your eyes.

For some of us our hearing plays another key role, allowing us to perform echo location. Echo location is a means to use hearing to determine the location and properties of an object in space, and is used by animals such as bats, dolphins, whales, shrews and some birds. The basic principle involves sound waves bouncing off objects. When the sound wave bounces off of an object it can be heard as an echo, and the location, size and shape of an object can be determined. Though they are not blind, bats use echo location to find food (usually small insects), and can detect objects as thin as a human hair in complete darkness.

In the human world, some of us blind folk use echo location as a means to navigate our surroundings, locate people and objects, and to quickly react in situations where safety is a concern, for example in the presence of an oncoming vehicle or when navigating an environment with a number of obstacles. Echo location isn’t usually something that comes naturally and takes a significant amount of training to perfect. It is usually developed throughout early life when a person cannot learn about their environment using vision, thus developing passive echo location to compensate.

When echo location is developed, it allows a person to detect the properties of almost any solid physical object, including people. A common misconception is that echo location requires the person to make small sounds, usually a clicking sound made with the tongue, in order to generate echoes. This is generally known as active echo location and is similar in principle to active sonar. For some, myself included, this isn’t the case. Very few environments are perfectly silent and it’s usually possible to detect echo using only the present background noise, or the sounds around you such as quiet background music, the sound of an appliance or even someone speaking. This is technically passive echo location.

Objects can be detected from quite a distance, the distance increasing the more you develop the skill. For example, if I stand roughly 1.5 metres away from a solid wall, with either ear directly facing the wall, I can ‘hear’ its presence. Moving closer allows me to get a reasonable idea of the height of the wall, and how far it extends in either direction, though my ability to locate behind me is somewhat limited. In some environments I am able to locate further. For example if I were to stand in a large hall measuring several metres square, I would be able to determine the location of the walls, the height of the ceiling and possibly even the doorways too.

Locating smaller objects often requires that I get closer to them. For example, I am currently sat at a desk with a keyboard directly in front of me, a cup of tea about 30CM behind that, and a laptop sitting on a stand approximately 60CM to my left. The stand rises the laptop off the desk by approximately 20CM. If I lean forward such that my head is in line with the keyboard, I am able to locate the laptop using my left ear. If I lean downward and tilt my head to the right, I can pinpoint the exact location and approximate size of the cup and the orientation of its handle. As the keyboard is extremely thin I am unable to distinguish it from the surface of the desk using echoes alone, though the desk (being large) is very easy to detect from almost any position in the room.

These objects are pretty small however. If I sit in front of my drum kit on which are mounted 5 cymbals roughly 14” in diameter and spread before me in a semicircle, spanning a distance of approximately 1.6 metres with the start and end points just behind each ear, I am able to determine the location of each cymbal by moving my head in a slight left-to-right motion. I can also locate the drums in a similar arrangement beneath. A long wall is situated directly in front of the drum kit, and the background noise of the room itself allows echoes to bounce off of that wall as well as the various parts of the kit, making location easier.

Echo location is also useful in identifying, interacting and communicating with people. If a person stands in front of me, I am able to determine their approximate height and build, as well as whether they are standing side or face on. This is useful when meeting someone for the first time, or when someone is presenting you with an arm to offer a guide, as them walking close to either side with an elbow slightly extended is usually enough to locate them without them having to verbally announce their presence. If the environment is quiet or if the people are close enough, echo location allows me to determine their movements, for example if someone stands, changes their position in relation to me, or extends their hand for me to shake, to show me something or to pass me an object.

Not every environment is particularly suited to echo location. Environments with quiet backgrounds limit the amount of echoes that are naturally received. Some would make a noise in such an environment in order to trigger an echo, though if you’re in a large open space in the middle of nowhere there is little that can be heard as there will be few objects off of which the echo can bounce, besides the solid ground. Loud environments are similarly difficult. Large crowds and environments with loud music can severely limit the ability to echo locate, similar to how your vision is reduced in darkness until your eyes adjust. In such environments it is usually possible to detect the presence of objects that are in very close proximity (a glass in front of you on a table for example) or people who are close nearby, though the reach of your ability to locate usually extends to less than a metre or so in front of you and to either side, and even less behind, depending on how well your locating skills are developed.

Echo location does have a couple of minor downsides, though these are far outweighed by its advantages. When your echo location develops it becomes subconscious (much like breathing), and can make you feel more claustrophobic than usual in small or constricted spaces. In some cases it can also cause fright, particularly for those of us who suffer from anxiety. During times when anxiety is heightened and particularly when tired and the environment is quiet, a slight turn of the head can bring an object into the ‘location field’ as it were. This sudden apparition and the brain’s slowed reaction can cause a moment of panic, a bit like having somebody unexpectedly jump out on you from a hiding place. Standing in open spaces can sometimes be unpleasant too, particularly with fast-moving crowds. This is only really an issue when you don’t have a point of reference (a person next to you for example), and can usually be helped by echo locating the ground itself and using it as a focus point.

In general however, echo location really is the gift that keeps on giving. It enables me to locate and detail objects extremely quickly and to determine at least some of the physical properties of people and my environment that you would pick up on first sight. It enables me to navigate familiar buildings with ease, and even comes in handy when I need to locate a misplaced object – the remote control on the sofa to my right, for example.

It is my hope that this article has been an informative read. Further reading can be found in this WikiPedia article. I aim to publish a number of future articles similar to this one, so if you’ve enjoyed this little glimpse into this blind guy’s mind be sure to check back regularly or follow my social media to be informed of future content. Any comments, questions or suggestions are welcome via the comments below or on social media. Until then…