There are times when we listen to a tune or a recording and we are just mesmerized by it. We think about the recording continuously- the voices, the tunes, the background music – all come together to create something this outstanding. But are these all? There are so many factors that work together to create a recording that they remain intertwined. One of those important factors is a Signal-to-Noise ratio (SNR).
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What is SNR?
The SNR is the measurement of desired and undesired sound. It measures how much-desired sound is present in the recording. The undesired sounds are external noise like traffic, electric static from equipment, voice murmur, and other background noises. They are expressed in the measurement of decibels (dB) and this SNR is very important.
If you record music or anything, you know how annoying background sounds are. They diminish the quality of the music and the clarity is ruined. The higher the SNR, the better the quality.
For instance, an SNR of 100 dB is better than 60 dB. It means the level of the audio signal is 100 dB more than the noise. SNR can be used in any form of signal transmission. You can measure the ice cores’ level of isotope, source units, and clarity of audio.
Where is SNR Used?
A detailed description of the SNR is found in products that deal with the audio function. Like the telephones, microphones, headphones, speakers, radios, amplifiers, receivers, turntables, CD, DVD, phones, tablets, etc. Even though it is recommended to make the specifications known, some manufacturers opt not to. In that case, you can determine the SNR by yourself.
For Mac OS X, click on the Wi-Fi indicator on the menu bar. Then take the value of the noise and then subtract it from the RSSI. Then you will get your SNR value. The RSSI is called Received Signal Strength Indicator. This measures how well your device can detect a signal from the router or access point. This value is found from the device’s Wi-Fi card. 55 is considered a good RSSI value.
Values of SNR
Let’s look at the values of SNR (all the values are in dB):
5 to 10: This is lower than the minimal level. At this level, you can’t really set a connection because the level of noise can is distinguished from here.
10 to 15: At this level, you can form a connection but then it won’t be reliable enough.
15 to 25: At this level, you can establish a poor connection.
25 to 40: This level is considered to be moderate.
41 or higher: This level is deemed to be great.
We have understood so far that the SNR affects all kinds of wireless networks. These all work through radio signals. So, all of them have maximum channel capacity.
With the increase of SNR, the channel capacity also increases. There is a formula through which you can measure the noisy channel data rate. With that, you can know what level of SNR is needed. This is known as Shannon’s law:
C = W log2(1 + )
The signal power that is received average is S”’
The noise power in average is ‘N’
The bandwidth is ‘W’ (Hertz)
How to Improve SNR
There are ways we can maximize the SNR for any scenario:
There is an internal electronic sound of the recording equipment called ‘noise floor’. This noise floor is present in every electrical device. They are not audible to human ears. There is a hissing sound that you will be able to hear if you turn up the volume of your television on an empty channel. That hissing sound is the noise floor. The noise floor gets canceled with the incoming audio signal. This audio signal is higher than the noise floor.
This is why we can’t hear the unwanted noise. This is called a good SNR. Then again, if the incoming signal is low and weak, then it can’t cancel the noise floor. This is an example of a bad SNR. This is why you need to choose a good device with a low noise floor especially in the case of the microphone. The low noise floor allows the user to hold a strong signal above the noise floor. This in turn achieves an excellent Signal-to-Noise ratio.
When the signal level reaches near the noise floor, it is determined as corruption. When this happens, the sender needs to retransmit frames back to the receiver. These retransmissions decrease the airtime. The wireless network slows down. So, it is recommended to aim for higher SNR.
20 dB or greater is determined as a good SNR. The higher the number gets, the better the Signal-to-Noise ratio. For voice-over Wi-Fi, the recommended is 25 dB because more interference is introduced here and it reduces the SNR. The noise floor is determined by an in-built NIC. You can get the SNR value by using a spectrum analyzer.
Another important factor that contributes to the SNR is the placement of the microphone. For capturing a strong signal, you will need a steady environment and a good microphone. The placement of the microphone often gets ignored compared to the quality. People focus on the equipment. But the placement is equally important. It has a significant effect on the SNR.
The SNR is better when the placement is closer to the sound source. The surroundings also have a great influence on the SNR. In a time of recording always listen to the environment. There is the sound of talking, wind, moving water sources, HVAC blowers. These are persistent sounds. They decrease the SNR by increasing the noise floor. In times like these, you need to shut the equipment which is making the sound. You can also change the sound source.
Sound quality is extremely important in any sort of recording. You don’t like background noises in any videos you watch or audios you listen to. They ruin the whole quality. Signal-to-Noise ratio is important in this regard. They make sure to cancel all the unwanted background noise and give us a perfect recording. It is important to have knowledge about the SNR so that we can ensure proper recordings.