Tag: physics

Audio Adversarial speech-to-text

I don’t usually go in for detailed technical papers on stuff that’s not directly relevant to what I’m working on, but I made an exception for this. Here’s the abstract:

We construct targeted audio adversarial examples on automatic speech recognition. Given any audio waveform, we can produce another that is over 99.9% similar, but transcribes as any phrase we choose (at a rate of up to 50 characters per second). We apply our white-box iterative optimization-based attack to Mozilla’s implementation DeepSpeech end-to-end, and show it has a 100% success rate. The feasibility of this attack introduce a new domain to study adversarial examples.

In other words, the researchers managed to fool a neural network devoted to speech recognition into transcribing a phrase different to that which was uttered.

So how does it work?

By starting with an arbitrary waveform instead of speech (such as music), we can embed speech into audio that should not be recognized as speech; and by choosing silence as the target, we can hide audio from a speech-to-text system

The authors state that merely changing words so that something different occurs is a standard adverserial attack. But a targeted adverserial attack is different:

Not only are we able to construct adversarial examples converting a person saying one phrase to that of them saying a different phrase, we are also able to begin with arbitrary non-speech audio sample and make that recognize as any target phrase.

This kind of stuff is possible due to open source projects, in particular Mozilla Common Voice. Great stuff.
 

Source: Arxiv

In a dark place

Last year, I remember being amazed by how black a new substance was that’s been created by scientists. Called Vantablack, it’s like a black hole for light:

Vantablack is genuinely amazing: It’s so good at absorbing light that if you move a laser onto it, the red dot disappears.

However, it turns out that Mother Nature already had that trick up her sleeve. Birds of Paradise have a similar ability:

A typical bird feather has a central shaft called a rachis. Thin branches, or barbs, sprout from the rachis, and even thinner branches—barbules—sprout from the barbs. The whole arrangement is flat, with the rachis, barbs, and barbules all lying on the same plane. The super-black feathers of birds of paradise, meanwhile, look very different. Their barbules, instead of lying flat, curve upward. And instead of being smooth cylinders, they are studded in minuscule spikes. “It’s hard to describe,” says McCoy. “It’s like a little bottle brush or a piece of coral.”

These unique structures excel at capturing light. When light hits a normal feather, it finds a series of horizontal surfaces, and can easily bounce off. But when light hits a super-black feather, it finds a tangled mess of mostly vertical surfaces. Instead of being reflected away, it bounces repeatedly between the barbules and their spikes. With each bounce, a little more of it gets absorbed. Light loses itself within the feathers.

Incredible.

Source: The Atlantic