* Posts by Hanry_M

1 post • joined 30 Jan 2018

When you play this song backwards, you can hear Satan. Play it forwards, and it hijacks Siri, Alexa


On the topic of ultrasound...

Kudos to the Register for getting 90% of a story across in very few paragraphs.

I would not normally grinch over the sentence “a microphone capable of suppressing ultrasound” but it leads to a couple of observations:

1) Microphones can be designed to suppress ultrasound, but that either makes them bulky or expensive. More likely the suppression is happening in the amplifier stage.

Interestingly, even this is an expense that scale-producers avoid as we found to our astonishment when we ran a hack-day around nature exploration: trying to use off the shelf gadgets to listen to bats. We found that out of several laptops and mobile phones about half had no hardware limitations limiting the frequency range to the human-audible spectrum! Not surprising, given that hugely oversampling and filtering in the digital domain is working fine, but I digress. Anyway, the observation was that the cheaper the laptop of phone the easier it was to hack it for bat-listening.

So, for money reasons alone, how much would you like to bet that even in three years’ time plenty of connected microphones will still be responding to ultrasound input?

2) Ultrasound is actually wanted by gadgets: digital fingerprinting of music, advertisements etc. has been reported aplenty recently, even in the Register iirc. Another reason to doubt that ultrasound will be ignored by connected mics.

More likely that gadgets will increase their listening range (“to better listen out for your protection” says grandma and we all feel comforted) and countermeasures will have to evolve in the signal processing. Where the success-rate will be unknown, and thus it ever bumbles on... :)

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