The 'whoosh' sound made by planes and helicopters passing overhead is not just due to the Doppler effect, but also due to comb filtering and ground echo. The sound is caused by two copies of the same sound arriving at slightly dif...
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Oona, a computer geek from Finland, shares her joy of researching signals, programming, and music on her blog absorptions.
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0Ultrasonic investigations in shopping centres
2024-06-09 •
The blog post explores the phenomenon of near-ultrasonic 'beacons' or pilot tones used in PA systems, particularly in shopping centers. These tones, often around 20 kHz, are used to monitor the health of multi-loudspeaker systems....
The blog post explores the audio imperfections in the soundtrack of the 1928 cartoon Steamboat Willie, which recently entered the public domain. The author investigates the presence of 'flutter' distortion, an unstable playback or...
0Using HDMI EMI for fast wireless data transfer
2023-02-27 •
The blog post explores the phenomenon of electromagnetic interference (EMI) from HDMI cables, which can be used for wireless data transfer. The author, Oona, discovers that certain monitors emit signals that can be intercepted and...
0Spiral spectrograms and intonation illustrations
2021-11-28 •
The blog post explores innovative methods for visualizing harmony, intonation, and overtones in music, focusing on the limitations of traditional spectrograms. The author discusses using equal temperament cents against time to ana...
0Speech to birdsong conversion
2021-03-29 •
The blog post explores the concept of converting human speech into birdsong, specifically blackbird song. The author describes a dream where a blackbird spoke in human language, which inspired the idea of transforming speech into ...
The blog post discusses the author's exploration of visual patterns in music using a vinyl record with a unique wavy pattern. The author discovered that the pattern was related to the tempo of the music and created a script to plo...
The blog post is a project diary by Oona, detailing her attempts to capture live video from a 1985 Nintendo NES console using a 2013 MacBook and existing hardware. She explores various methods, including using a capture device, fi...
0Beeps and melodies in two-way radio
2019-03-15 •
The blog post by Oona focuses on her recent exploration of two-way FM radio, particularly the PMR446 frequency band used for short-distance UHF walkie-talkies. She discusses the automatic monitoring and visualization of multiple c...
0Animated line drawings with OpenCV
2017-12-30 •
The blog post discusses using OpenCV, a C++ computer vision library, to create animated line drawings and video art for a music project. The author explains the process of setting up an OpenCV project, drawing basic shapes, and ap...
0In pursuit of Otama's tone
2017-11-25 •
The blog post explores the challenges and solutions in creating a virtual instrument that mimics the sound of the Otamatone, a unique musical instrument with a touch-sensitive slider. The author discusses the complexities of the O...
The blog post discusses voice inversion, a method used to make speech unintelligible to prevent eavesdropping. The author introduces a software tool called 'deinvert' that can reverse this process, including a more advanced method...
0Gramophone audio from photograph, revisited
2017-07-27 •
The blog post discusses the author's attempt to recover analog audio from a toy robot's miniature vinyl record using a digital camera. The author revisits previous efforts with a slightly improved method, using an old photo of the...
0Virtual music box
2017-07-17 •
The blog post describes the author's journey in creating a virtual music box instrument. The author faced challenges with a physical music box that only played notes on the C major scale and decided to digitize the sound to create...
The blog post explores the concept of radio fingerprinting using CTCSS (Continuous Tone-Coded Squelch System) in hand-held FM transceivers. The author investigates the potential of using CTCSS tones to identify unknown radio trans...
0Redsea 0.7, a lightweight RDS decoder
2016-10-02 •
The blog post discusses the latest updates and features of Redsea, a lightweight RDS decoder project. The author explains the input and output formats supported by Redsea, including FM multiplex carrier demodulation and ASCII bina...
0Pea whistle steganography
2015-10-06 •
The blog post explores the concept of embedding data within the sound of a pea whistle, specifically the Acme Thunderer 60.5. The author investigates the frequency modulation caused by the pea inside the whistle and considers the ...
0The microphone bioamplifier
2015-10-02 •
The blog post discusses the author's attempt to detect EMG signals from facial muscles using a homemade bioamplifier setup. Lacking professional equipment, the author improvises with household items to create conductive gel and el...
0Case study: tinnitus with distortion
2015-07-11 •
The blog post explores a personal case study of low-frequency tinnitus with distortion, which the author experiences. The author discusses the peculiarities of this tinnitus, including its potential subtype related to joint proble...
0Trackers leaking bank account data
2015-04-14 •
The blog post discusses a Finnish online bank that used a US-based third-party analytics script, raising privacy concerns. The script collected user data, including IP addresses, URLs, and potentially bank account numbers, which c...
0Receiving RDS with the RTL-SDR
2015-02-08 •
The blog post discusses the development and functionality of redsea, a command-line RDS decoder initially created to decode RDS from demultiplexed FM stereo sound. The author has expanded its capabilities to support the RTL-SDR te...