# acoustics Published articles for acoustics. This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles. ## Speech to birdsong conversion DevFeed: [Speech to birdsong conversion]() Original publisher: [Read original article]() Author: Oona Räisänen (noreply@blogger.com) Published: 2021-03-29T18:37:00Z Content type: tutorial Language: en Sources: [Oona Räisänen]() Topics: [Perl](), [Command-line interface](), [toolchain](), [Code]() Tags: [acoustics](), [art](), [command-line](), [dreams](), [perl](), [programming](), [script](), [sound](), [synthetic](), [toolchain](), [voice]() ### AI overview This article presents a proof-of-concept method for converting speech into synthetic blackbird song. It describes extracting speech frequency and amplitude with FM and AM demodulation, multiplying the frequency while preserving amplitude variation, and implementing the process with a Perl-SoX-csdr command-line toolchain. ### Source excerpt I had a dream one night where a blackbird was talking in human language. When I woke up there was actually a blackbird singing outside the window. Its inflections were curiously speech-like. The dreaming mind only needed to imagine a bunch of additional harmonics to form phonemes and words. One was left wondering if speech could be transformed into a blackbird song by isolating one of the harmonics... One way to do this would be to: Find the instantaneous fundamental frequency and amplitude of the speech. For example, filter the harmonics out and use an FM demodulator to find the frequency. Then find the signal envelope amplitude by AM demodulation. Generate a new wave with similar amplitude variations but greatly multiplied in frequency. A proof-of-concept script using the Perl-SoX-csdr command-line toolchain is available (source code here). The result sounds surprisingly blackbird-like. Even the little trills are there, probably as a result of FM noise or maybe vocal fry at the end of sentences. I got the best results by speaking slowly and using exaggerated inflection. Someone hinted that the type of intonation used in certain automatic announcements is perfect for this kind of conversion. And it seems to be true! Here, a noise gate and reverb has been added to the result to improve it a little: And finally, a piece of sound art where this synthetic blackbird song is mixed with a subtle chord and a forest ambience: Think of the possibilities: A simultaneous interpreter for talking to birds. A tool for dubbing talking birds in animation or live theatre. Entertainment for cats. What other birds could be done with a voice changer like this? What about croaky birds like a duck or a crow? (I talked about this blog post a little on NPR: Here's What 'All Things Considered' Sounds Like -- In Blackbird Song) ## Pea whistle steganography DevFeed: [Pea whistle steganography]() Original publisher: [Read original article]() Author: Oona Räisänen (noreply@blogger.com) Published: 2015-10-06T22:54:00Z Content type: article Language: en Sources: [Oona Räisänen]() Topics: [Steganography](), [data]() Tags: [acoustics](), [audio](), [embedding](), [measurement](), [physics](), [shower-thoughts](), [signal](), [silly]() ### AI overview The article investigates whether a pea whistle's frequency modulation can carry hidden data. It analyzes recordings and spectrograms, finds that the modulation could fit frequency-shift keying, and describes synthesizing a whistle-like signal with a data-dependent phase modulator and harmonics. ### Source excerpt Would anyone notice if a referee's whistle transmitted a secret data burst? I do really follow the game. But every time the pea whistle sounds to start the jam I can't help but think of the possibility of embedding data in the frequency fluctuation. I'm sure it's alternating between two distinct frequencies. Is it really that binary? How random is the fluctuation? Could it be synthesized to contain data, and could that be read back? I found a staggeringly detailed Wikipedia article about the physics of whistles - but not a single word there about the effects of adding a pea inside, which is obviously the cause of the frequency modulation. To investigate this I bought a metallic pea whistle, the Acme Thunderer 60.5, pictured here. Recording its sound wasn't straightforward as the laptop microphone couldn't record the sound without clipping. The sound is incredibly loud indeed - I borrowed a sound pressure meter and it showed a peak level of 106.3 dB(A) at a distance of 70 cm, which translates to 103 dB at the standard 1 m distance. (For some reason I suddenly didn't want to make another measurement to get the distance right.) Later I found a microphone that was happy about the decibels and got this spectrogram of a 500-millisecond whistle. (HTML5 audio: The sound of a whistle.) The whistle seems to contain a sliding beginning phase, a long steady phase with frequency shifts, and a short sliding end phase. The "tail" after the end slide is just a room reverb and I'm not going to need it just yet. A slight amplitude modulation can be seen in the oscillogram. There's also noise on somewhat narrow bands around the harmonics. The FM content is most clearly visible in the second and third harmonics. And seems like it could very well fit FSK data! Making it sound right I'm no expert on synthesizers, so I decided to write everything from scratch (whistle-encode.pl). But I know the start phase of a sound, called the attack, is pretty important in identification. It's simple t ## Case study: low-frequency tinnitus with distortion DevFeed: [Case study: low-frequency tinnitus with distortion]() Original publisher: [Read original article]() Author: Oona Räisänen (noreply@blogger.com) Published: 2015-07-11T07:39:00Z Content type: article Language: en Sources: [Oona Räisänen]() Topics: [Simulation](), [Compression]() Tags: [acoustics](), [analysis](), [biohack](), [case-study](), [compression](), [html5](), [simulation]() ### AI overview The author analyzes periodically appearing low-frequency tinnitus, including simulated audio and occasional frequency shifts. The article speculates that a near-sinusoidal 65 Hz tone could cause perceived speech distortion through amplitude modulation or heterodyning, while noting that the condition is poorly understood. ### Source excerpt A periodically appearing low-frequency tinnitus is one of my least favorite signals. A doctor's visit only resulted in a WONTFIX and the audiogram shown here, which didn't really answer any questions. Also, the sound comes with some pecularities that warrant a deeper analysis. So it shall become one of my absorptions. The possible subtype (Vielsmeier et al. 2012) of tinnitus I have, related to a joint problem, is apparently even more poorly understood than the classical case (Vielsmeier et al. 2011), which of course means I'm free to make wild speculations! And maybe throw a supporting citation here and there. Here's a simulation of what it sounds like. The occasional frequency shifts are caused by head movements. (There's only low-frequency content, so headphones will be needed; otherwise it will sound like silence.) (HTML5 audio: computer-generated low-frequency tone on the right channel with some frequency shifts.) It's nothing new, save for the somewhat uncommon frequency. Sounds a bit like a car left idling outside the house. Now to the weird stuff. Real-life audio artifacts! This analysis was originally sparked by a seemingly unrelated observation. I listen to podcasts and documentaries a lot, and sometimes I've noticed the voice sounding like it had shifted up in frequency, for just a small amount. It would resemble an across-the-spectrum linear shift that breaks the harmonic relationships, much like when listening to a SSB transmission. (Simulated sound sample from a podcast below.) [HTML5 audio: excerpt from a science news podcast with distorted speech.] I always assumed this was a compression artifact of some kind. Or maybe broken headphones. But one day I also noticed it in real life, when a friend was talking to me! I had to ask her repeat, even though I had heard her well. Surely not a compression artifact. Of course I immediately associated it with the tinnitus that had been quite strong that day. But how could a pure tone alter the whole spectrum so d