Scientists found a way to make sound travel in only one direction | Hacker News Reader

Scientists found a way to make sound travel in only one direction

zmescience.com

77 pointsBrajeshwar18 comments

This is different mechanism from the sound laser or SASER. The sound laser works like a laser, with a cavity where particles are bounced back and forth to stimulate a highly coherent beam of waves.

I’m not sure if this new mechanism is definitely better than the existing sound laser?

This seems to be similar to a microwave circulator. https://en.wikipedia.org/wiki/Circulator

I was curious as cousin commenters, and this helped make sense of things (and connect a few completely unrelated intuitions)

  As long as the effects of viscosity and diffusion are negligible, the fluid in a moving vortex is carried along with it. In particular, the fluid in the core (and matter trapped by it) tends to remain in the core as the vortex moves about. This is a consequence of Helmholtz's second theorem. Thus vortices (unlike surface waves and pressure waves) can transport mass, energy and momentum over considerable distances compared to their size, with surprisingly little dispersion. This effect is demonstrated by smoke rings and exploited in vortex ring toys and guns.

https://en.wikipedia.org/wiki/Vortex#Evolution

I read the article and still don’t get it. Anyone want ELI5?

They used a concave disk-like speaker to produce sound. This solid shape makes the sound waves kind of spin around themselves like a tornado or one of those bubble rings you see people blow underwater [1] instead of a normal pressure wave that goes in all directions.

The tornado sound wave can only move forward and once it hits something is dissipated and doesn't reflect the sound.

1. https://youtu.be/t2kvEC852MI?si=QJjinL7AK6ZZS_SO

I've only skimmed the article/paper and I also dont' understand, so I'm just as ignorant as you, but there is such a thing as a Tesla valve that is a static object that allows water to flow in one direction [0]. I would assume that maybe they can make little vortices of air/liquid (as the comment by kylebenzle suggests) that are dynamic and create a similar structure as it evolves.

[0] https://en.wikipedia.org/wiki/Tesla_valve

It is a hotel revolving door for sound waves.

But the door is also a sound wave.

Audible laser?

Line of sight audio would be wonderful in a crowd.

So could this be used at festivals and stuff to direct the sound only to the audience?

see: https://news.ycombinator.com/item?id=41816544

I've met people who can do that.

I just want a way to not hear my neighbor's 10 yo bounce a basketball for 3 hours a day

Have to wait for them to discover girls, or boys...

Classical music while you're outside

Newly re-invented, quiet, airless 3D printed Basketballs, if you were so fiscally inclined.

We already knew a way - a shockwave

A shockwave does not travel linearly.

It does?

https://en.m.wikipedia.org/wiki/Shock_tube#/media/File%3ASho...

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