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What Is SPL For A PA System

Aug 08,2023 | Murphy

SPL measures these air pressure variations and quantifies how intense or loud the sound is. It is commonly used to describe the loudness of audio equipment, environmental noise, and other sound-related phenomena. Therefore, It's important to check this index when you are going to buy a PA system.

It is generally understood that a sound energy doubles for every 3dB increase, and due to the non-linear relationship of the human ear's perception of loudness, a typical increase of 10dB is required for doubling the perceived loudness.

Here is a detailed explain for it ----- If I have a speaker with a sensitivity of 100 decibels, to increase the sound output to 103 decibels, I need to double the power. Therefore, this speaker would require 2 watts to produce 103 decibels, 4 watts for 106 decibels, 8 watts for 109 decibels, and 10 watts for 102 db. You can begin to understand why getting a speaker to play very loudly requires a substantial amount of power. You can check this photo if you are not clear.

Double or twice the loudness = factor 2 means about 10 dB more sensed loudness level (psycho acoustic)
Double or twice the voltage = factor 2 means 6 dB more measured voltage level (sound pressure level) 
Double or twice the power = factor 2 means 3 dB more calculated power level (sound intensity level)

In this way, if the initial SPL measurement at the party is 90 dB. Now, if the band decides to crank up the volume, and this SPL increases to 100 dB, it might seem like just only a 10 dB difference. However, in reality, that 10 dB increase represents a sound that is 10 times more intense!

Now, let's assume you move closer to the stage, and your new SPL measurement is 110 dB. This might seem like a 10 dB difference from the previous measurement of 100 dB. However, once again, this actually signifies that the sound has intensified tenfold compared to the 100 dB level.

So, SPL provides a way to quantify and compare the intensity of sound. It's logarithmic nature reflects how our ears perceive loudness. Small changes in decibels can correspond to significant changes in how we hear and feel sound.

All in all, If the maximum SPL of a speaker is calculated using estimated maximum power and rated sensitivity values, then, no, it might not be very accurate. If the maximum SPL is calculated by measuring the actual volume from 1 meter away using precise sensitivity figures, then this data would be quite accurate. This is why I told you that you can use SPL to judge and select the audio equipment you desire.

However, it's worth noting that you shouldn't solely rely on SPL as the sole reference standard, as many manufacturers often use theoretical figures to calculate the maximum SPL of their products. In this regard, SPL can only possess a certain level of reference credibility. Regardless, in today's article, we've elaborated on SPL and the significance it represents, which should provide some assistance in your selection of the desired PA SYSTEM.