Echoes, as Explained by Dummies

human echolocation

Whether you're a student doing homework or a curious grown-up, the internet has long since replaced that shelf of encyclopedias in the library as the go-to source of information. We think the obvious problem is that the people who wrote those encyclopedias either knew what they were talking about or ran their words past someone who did. Content-farm freelancers on the internet? Not so much. That's why there's so much ignorant prose at places like eHow.com. That's where we found Sophia Sola (sometimes known as Sophie Strosberg) attempting to explain "How Are Echoes Made?"¹

Sola / Strosberg opened by telling her readers what sound is:

"Sound waves are invisible waves that carry sound from its origin into the surrounding environment, whether there is anyone around to hear it or not. "

...umm, yeah: "invisible." Well, sure -- but could you be more specific? After all, radio, microwaves, and light are all "invisible waves." Is sound the same? (hint: the answer to that question is, "No.")

Sophia / Sophie continues in this vein, further explaining that

"Echoes are made when sound waves bounce off a surface and are reflected back to your ears."

Good job, Sophie! That's correct! Can you give us more information? Sure you can...

"It's not possible to distinguish between the sound waves directly from the source, and the sound waves that come from a reflection, because sound moves so quickly—unless, that is, the reflective surface is at least about 75 meters away."

For you people who have problems with the metric system, 75 meters is a tad under 250 feet. To say that echoes are indistinguishable from the source unless "the reflective surface is at least about 75 meters away" is utter bullshit: bats and some blind people use echolocation at distances far smaller than 75 meters. Sola / Strosberg entirely neglects any discussion of the "quality" of the original signal vs. an echo, except for a throwaway comment saying that smooth surfaces are "more likely to direct waves to your ear" than rough surfaces. That's utter bullshit, too, as bats know: (almost) every surface reflects sound, some are better than others, and the quality of that reflected sound is key to using echolocation to describe the reflector. Sheesh.

Instead of a discussion of what happens to the wavelength, amplitude, phase and frequency of sound waves when they're reflected, Sophie wanders into describing places where you might expect an echo: caves, mountains, big rooms. She even veers into saying that bats use sonar "to see."

With just the barest mention of how echoes form (the original question, in case you forgot) and lots of information at the kindergarten level of science, Sola utterly failed her audience – and you know what that earns her: the Dumbass of the Day.

¹ Seems like Leaf Group is following us around to clean up its mess. the original text (now deleted) can be found with archive.org's Wayback machine; its URL was  ehow.com/about_7222124_echoes-made_.html

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