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posted by chromas on Wednesday July 10 2019, @10:24AM   Printer-friendly
from the Madame-dum-die-dum-dum-Defarge dept.

ETH Zurich:

To store the data, the two doctoral students and their colleague, Master's student Gabriel Voirol, make minimal changes to the music. In contrast to other scientists' attempts in recent years, the researchers state that their new approach allows higher data transfer rates with no audible effect on the music. "Our goal was to ensure that there was no impact on listening pleasure," Eichelberger says.

Tests the researchers have conducted show that in ideal conditions, their technique can transfer up to 400 bits per second without the average listener noticing the difference between the source music and the modified version (see also the audio sample). Given that under realistic conditions a degree of redundancy is necessary to guarantee transmission quality, the transfer rate will more likely be some 200 bits -- or around 25 letters -- per second. "In theory, it would be possible to transmit data much faster. But the higher the transfer rate, the sooner the data becomes perceptible as interfering sound, or data quality suffers," Tanner adds.

The researchers from ETH Zurich's Computer Engineering and Networks Laboratory use the dominant notes in a piece of music, overlaying each of them with two marginally deeper and two marginally higher notes that are quieter than the dominant note. They also make use of the harmonics (one or more octaves higher) of the strongest note, inserting slightly deeper and higher notes here, too. It is all these additional notes that carry the data. While a smartphone can receive and analyse this data via its built-in microphone, the human ear doesn't perceive these additional notes.

[...] To tell the decoder algorithm in the smartphone where it needs to look for data, the scientists use very high notes that the human ear can barely register: they replace the music in the frequency range 9.8-10 kHz with an acoustic data stream that carries the information on when and where across the rest of the music's frequency spectrum to find the data being transmitted.

Eichelberger M, Tanner S, Voirol G, Wattenhofer R: Imperceptible Audio Communication[pdf]. 44th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Brighton, 12-17 May 2019


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  • (Score: 2) by Rupert Pupnick on Wednesday July 10 2019, @02:58PM

    by Rupert Pupnick (7277) on Wednesday July 10 2019, @02:58PM (#865390) Journal

    Agree with your comments, and would add that the average listener today is probably using earbuds, and as such, I would not put a lot of credence in their assessment.

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