Converting from analog to digital. Sound is a wave, and therefore to record it accurately, the recording device needs to be able to allow for the continuous change in frequency and amplitude. Recording mediums such as tape and vinyl allow this to happen. However, both of these formats can degrade over time. A digital version of the sound can however be created by taking samples of the sound. To do this, a microphone will translate the change in air pressure into an electrical voltage.
This in turn will be converted into bytes of information that could be understood by the computer. To create an accurate digital version of a sound, many samples are taken. each sample is assigned a particular binary number with each representing the sound at a particular point in time. by something is saying thousands of times per second. It is possible To build up an accurate representation of the sound, the less you sample, the less the digital version will be to the actual sound. In turn, this means the more you sample, the closer the digital version will be.
However, this will also impact on how large file sizes, sample rate is measured in hertz, and this is a measurement of the amount of samples that are taken per second. A common rate for high quality music is 44,100 samples per second. as we did with images, we will be calculating file size of sound files. To do this, we need to know the bitrate. This is a measurement of how many bits are being processed per second for the digital send. to work out the bid rate, you need to know how many samples are being taken per second, which is called the frequency and how many bits are being used per sample and the number of channels being used.
In images we saw that the number of bits used impacted the Upon the number of colors that could be represented, the number of bits used in each sound sample will affect how finely tuned that sample is to the sound that was being recorded. High quality files usually have 44,100 samples per second, using 16 bits per sample, and two channels of stereo audio. However, you will be told the relevant information in questions if you're required to carry out a calculation. Once you know the bit rate to calculate the file size of an audio file, you need to multiply the bitrate by the length of the audio. So for high quality tracks 30 seconds the file size would be 1,411,200 times 30, which equals 42,336,000 bits or 5.2 19 megabytes once it's been converted. Now it's your turn to try and question you may want to reference the previous tests.
In order to help you out, remember, you need to calculate the bitrate before you can calculate the file size. To calculate the bitrate, we need to multiply 300, which is the number of samples per second by four, which is the bit depth by one, which is the number of channels used. This gives us 1200 bits per second, the audio file was 20 seconds long. So to calculate the file size in bits, we do 1200 times 20, which is 24,000 bits. We were asked to work this out in bytes. So to go from bits two bytes we need to divide by eight.
So 24,000 divided by eight gives us 300 bytes. Another question for you to try. Please remember to pause the video whilst you have a go. This time to calculate the bitrate we need to multiply 5000 which is the number of samples per second by 32, which is the bit depth by the number of channels, which is two 5000 times 32 times two gives us 320,000 bits per second. The audio file was 200 seconds long. So 320,000 multiplied by 200 gives us 64 million bits.
We were asked to calculate this in megabytes. So to go from bits two bytes, we divide by eight, which gives us 8 million bytes. To go to kilobytes, we divide by 1000, which gives us 8000 kilobytes. And to go two megabytes, we divide by 1000, which gives us eight megabytes