Video Discription |
In this video, I will look at Sound Recording Equipment. If you are planning on recording audio, depending on your requirements, you may need to purchase some sound recording equipment to get good results.
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Analog to Digital
To understand how sound equipment works, I will first look at the process of converting analog to digital. To understand this, I will first look at an analog wave. To convert the wave from analog to digital, there are two different measurements that are used on the wave. Changing the precision of these measurements will affect the quality the wave is recorded at.
The first characteristic measured is the sample rate. The sample rate is the number of times per second that the sound wave is measured. The second is the bit depth or sample depth. This is the resolution the sample is recorded at.
To understand how this works, consider that we have a sound wave that we want to convert to digital. To do this, first you need to decide what sample rate you want to use. This will determine how often the wave is measured. The next thing to consider is how the wave is measured. In this example, I will consider that 2 bits are used to measure the wave. You probably will use a lot more than 2 bits to measure a wave, but to make it easy to understand, I will use 2 bits.
To convert the wave to digital, the wave is measured, and the result stored using a 2-bit value. Essentially, the wave is measured, and the height of the wave is recorded. You can see that using 2 bits allows us to effectively record four different positions of the wave.
If I now compare the same wave, however this time using 3 bits, this will give us eight values. Notice that, when the wave is sampled using 3 bits, this gives a better result than for 2 bits, even using the same sample rate – notice that since there are more values, we can better represent the wave. Thus, the more bits you use the better results you will get.
In this case I have used 2 and 3 bits to illustrate the concept. In the real world, 8, 16 and 24 bits are commonly used. 16 bits is the standard for CDs. 24 bits is used for DVDs and professional equipment. More bits are better; however, this does increase the size required for the data file. With the amount of space that we have available nowadays, this is not generally a problem; however, for applications where size is a concern, 8 bits may be used. For example, when transmitting voice over a telephone line or for audio conferencing over a slow internet connection, the application may use a bit depth of 8.
So now that we have had a look at what the process of converting an analog wave to a digital wave is, I will next have a look at how we can work out how much space we will need.
Bit Rate
The number of bits required is measured as a bit rate. The bit rate is essentially the number of bits required for audio encoding per second. It is calculated by multiplying the frequency, bit depth and number of channels.
Let’s consider a typical example, such as what is used for encoding audio on a CD. The frequency is 44.1k, 16 bits for audio and two channels. This will give a result of 1,411 kilobits per second. If I apply this to a 240 second file, this will give a result of just over 40 Megabytes. So, we now have some idea of how to encode sound and how much space is required. The next step is to look at how we are going to record it.
Analog to Digital Converter (ADC)
Since audio is analog, you will need some way to convert the analog wave into digital. In order to do this, an analog to digital converter or ADC is required. This is a device that is connected between your microphone and the computer, that will convert analog to digital. The simplest solution is often to use the on-board sound adapter.
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References
“The Official CompTIA A+ Core Study Guide (Exam 220-1001)” Chapter 5 Paragraph 213 - 218
“CompTIA A+ Certification exam guide. Tenth edition” Pages x – x
“Sampling (signal processing)” https://en.wikipedia.org/wiki/Sampling_(signal_processing)
“Digital-to-analog converter” https://en.wikipedia.org/wiki/Digital-to-analog_converter
“Signal-to-noise ratio” https://en.wikipedia.org/wiki/Signal-to-noise_ratio
“Signal To Noise Ratio” https://www.youtube.com/watch?v=w4IcAkrNFn0
“Sound wave” https://www.pngfuel.com/free-png/aagog
“picture: bookcase” https://unsplash.com/photos/VNCz-57rm10
Credits
Trainer: Austin Mason http://ITFreeTraining.com
Voice Talent: HP Lewis http://hplewis.com
Quality Assurance: Brett Batson http://www.pbb-proofreading.uk |