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Sound pressure vs. sound power

Often, when we think of sound, we’re just talking about one thing – what we can hear. And for many of us, that’s enough for us in everyday conversation.

But sound isn’t a one-dimensional thing. 

In acoustic terminology, there’s a significant difference between sound power and sound pressure. And when it comes to situations such as nearby building works, buying your daughter a drum kit, or even buying a heat pump, these differences are important.

Knowing the difference between sound power and sound pressure can help to provide context to issues such as sound pollution – and it can help you to determine whether a new source of sound may cause disruption to your life.

What is sound pressure?

This is a physical measurement of the sound energy emitted from a source of noise. If you were standing in a large room with a dog barking, the sound pressure may be different depending on where in the room you are standing relative to the dog.

Sound pressure is actually measured in Pascal, but we most often see it expressed in decibels, or dBA, for reasons we’ll mention below.


What is sound power?

The sound power level is a theoretical measure of the sound a particular source emits, whether that’s a heat pump unit, a dog barking or a jet taking off. In other words, this is a property of the noise-emitting object itself, and doesn’t change depending on where you are in relation to said object.

Sound power is measured in Watts, but again, you’ll most often see it expressed in dBA.


Sound intensity

Additionally, you may come across sound intensity, which refers to the ‘flow’ of sound including its direction and level. 


Measuring sound 

While you may see sound pressure, sound power and sound intensity all referred to in decibels (dB), that isn’t the unit of measurement  it’s a unit of expression which helps us to interpret the relative quantities. 

Because sound power, pressure and intensity all use different units of measurement, they are converted into decibels to create a scale of reference which helps to compare those values. 

Below, we’ve included a table with some measurements of sound included, to give you a sense of how loud certain decibel counts are.

Lp dB(A) 

Perceived loudness 

Equivalent sound 


Threshold of hearing



Extremely soft

Rustling leaves, quiet room


Very soft

Refrigerator humming


Moderately loud

Normal conversation, restaurant


Very loud

City traffic, lorry


Extremely loud

Symphonic orchestra, farm tractor


Threshold of feeling

Jet taking off


Why do we need these measurements?

Sound pressure level can vary, dependent on distance, the position of the noise-emitting object and its environment, including reflections or reverberations from nearby surfaces. If you take your barking dog from inside your home to outside in your garden, the sound pressure will be different as a result of sound energy being dispersed into the atmosphere. 

When you’re thinking about choosing a heat pump, you might rightly consider whether it would be noisy and have an impact on your environment and home life. 

Daikin heat pumps are manufactured with our revolutionary near-silent technology, making them near undetectable. So you can experience all the benefits of renewable heat – without disruption to your lifestyle.

Explore the product pages to find out more about each of our unit’s technical specs, or get in touch with us for more information.


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