Recording a sampled audio signal is easy.
#MUSIC SHAZAM DJSILBERLINGTECHCRUNCH PROFESSIONAL#
(This specific rate was originally chosen by Sony because it could be recorded on modified video equipment running at either 25 frames per second ( PAL) or 30 frames per second (using an NTSC monochrome video recorder) and cover the 20,000 Hz bandwidth thought necessary to match professional analog recording equipment of the time.) So, when choosing the frequency of the sample that is needed to be recorded you will probably want to go with 44,100 Hz.
This is the sampling rate of Compact Discs, and is also the most commonly used rate with MPEG-1 audio ( VCD, SVCD, MP3). As a result, audio is most often recorded at a sampling rate of 44,100 Hz. The human ear can detect frequencies roughly between 20 Hz and 20,000 Hz. In particular, to capture all of the frequencies that a human can hear in an audio signal, we must must sample the signal at a frequency twice that of the human hearing range. The Nyquist-Shannon Theorem tells us what sampling rate is necessary to capture a certain frequency in continuous signal. Therefore, instead of a single conversion, an analog-to-digital converter performs many conversions on very small pieces of the signal - a process known as sampling The conversion involves quantization of the input, and it necessarily introduces a small amount of error. This is done by capturing a digital value that represents the amplitude of the signal. This continuous signal is not so useful in the digital world, so before it can be processed, it must be translated into a discrete signal that can be stored digitally. In a microphone, the first electrical component to encounter this signal translates it into an analog voltage signal - again, continuous. An actual sound wave in air is a continuous pressure signal. Recording devices mimic this process fairly closely, using the pressure of the sound wave to convert it into an electrical signal. Finally, the little hair cells produce electrical impulses, which are transmitted to our brain through the auditory ear nerve. When that vibration comes to our ears, particularly the eardrum, it moves small bones which transmit the vibration further to little hair cells deep in our inner ear. We know that in reality, sound is a vibration that propagates as a mechanical wave of pressure and displacement, through a medium such as air or water. What is sound really? Is it some sort of mystical material that we cannot touch but which flies into our ears and makes us hear things? In this article we’ll go over the fundamentals of Shazam’s music recognition algorithm. But how does Shazam work? Shazam’s algorithm was revealed to world by its inventor Avery Li-Chung Wang in 2003.
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