Why does the air 'squeak' in the Rivers Trail Labyrinth?

YOU ASKED:Located along the trail between Pioneer Park and Riverside Park is a circular, paving stone maze. When you stand at the centre of the maze and clap your hands, the air squeaks. If you step 10 feet in any direction and clap your hands, the squeak does not occur. Can you please find someone who can explain this phenomenon? Thank you so much.

- Shelley Hallock and Jasmine Johnston

OUR ANSWER:This may be the most fun Readers' Report we've done to date, but it hasn't been easy finding a definitive answer to your question.

Our first hint at an answer came via Twitter, from Thompson Rivers University's Environment & Sustainability department, who pointed us to City's website. There, we found a report by students at Ursinus College in Pennsylvania, who studied the sound patterns of a similar stone maze.

They discovered that the squeak produced by clapping had a lot to do with the bevel between each ring of stones. The sound of a handclap bounces off each bevel between concentric rings, returning to the centre at different speeds, which cause the sound reflections to interfere with each other and produce the squeak.

"It's certainly an interesting phenomenon," said Thompson Rivers University's Mark Paetkau, a senior physics lecturer.

But, Paetkau says he's torn between two possibilities.

The first involves pitch reflection - the theory posed by Ursinus College.

"The idea is the sound goes out and gets reflected back by the stones right where you are, but it arrives a little bit later than the clap," said Paetkau.

"So, if I clap my hands, the sound goes to my ears and it also goes out and comes back (to the centre of the labyrinth). When it comes back, it adds up to the sound coming from the original clap."

So, the sound delay causes a change in sound frequency heard at the centre of the labyrinth.

Paetkau's other theory proposes that a handclap produces many levels of frequencies traveling out from the centre of the labyrinth, the lowest of which dissipate as they travel outward, and the highest of which are reflected back by the bevels or ridges in the ring pattern of the stones.

"Of course, I have two competing theories in my mind and now I have to work out which one is actually correct."

Paetkau said he plans to test both theories in different circular settings, one of them being TRU's astronomy observatory.

In the meantime, readers can weigh in on the subject on The Daily News website or by emailing litt@kamloopsnews.ca. We've also produced a YouTube video of the interview with Paetkau, which can be seen on The Daily News YouTube channel.

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