What we mean by “noise” is simply the sound level (SPL), something that we perceive and measure with the sound level meter. We also stated that the noise in the larger room will be lower than this in the smaller one. We stated above that the SWL is something that belongs to the source and is independent of where the source is located. But before writing it right away, let’s analyze what is happening with our compressor from Figure 1 and the noise it is generating. Is there a relation between SWL and SPL? Yes, there is. An easy way is by going back to the article “Let's Talk Basics!” published in Canadian Audiologist where it was treated more extensively, including the concept of dBA). (You may want to refresh your knowledge of Sound Pressure and Sound Pressure Level. Quite large and difficult to manage, right? Transforming sound pressure to SPL implies the same mathematical procedure used for sound power that reduces this relation to only 120 decibels (dB). The relation between the weakest sounds pressure that we can hear and the one that can destroy our inner ear cells is almost 1:1,000,000.
Sound Pressure Level (SPL)Īnd now we are finally coming down to the SPL that is the expression most commonly used when dealing with sound. Here are some values of Sound Power and Sound Power Level: 3. SW0 is the reference power = 10 -12 W = 1 pW SW is the sound power of the same source in Watt and Where SWL is the sound power level of a source in dB For that purpose we use the decibel notation, where What about power level? Well, the same as with sound pressure, we like to compress the enormous range of sound power found in real life into something more manageable. In Figure 1B we have the same compressor (same sound power) in a larger room, where the sound level will be lower. Figure 1A shows our compressor in the small room. Not so if it is located in a large auditorium, since its sound power remains the same wherever the compressor is located (provided nothing internal changes). As an example, a small compressor located in a small room, will be quite noisy. As such, it describes the source and is independent of its surrounding. Sound power of a source is the total power emitted by that source in all directions. Sound power is the energy rate – the energy of sound per unit of time generated by a sound source. Sound is a mechanical wave and as such consists physically in oscillatory elastic compression and in oscillatory displacement of a fluid, generally air. It is described as a form of energy associated with the vibration or disturbance of matter. To better understand the concept of power, we will start by describing another basic concept – the acoustical energy. And, and the beginning, there are the definitions. As the philosophers in the antiquity used to do before getting into their long and deep discussions (at least that is what we are told so): let us start by the beginning. However, as a matter of fact, there is a lot in common between sound pressure and sound power. Nothing in common between both! That is true even in reality – there is nothing in common between tire pressure and rocket power. When thinking on power, I imagine the lifting of a spaceship aimed at the moon. Whenever I think on pressure, I see my finger pressing against the tire of my bicycle to see if it has the right pressure. The authors bemoaned the fact that the public was frequently confused at public meetings held in Quebec about this because they confused sound pressure and sound power… well, I too was confused so Alberto Behar was asked to unconfused me. In a recent issue, there was a discussion about the effects of wind turbines on people’s health. In my case, it’s the other CAA – the Canadian Acoustical Association (and yes, I am also a member of the Canadian Automobile Association as well).
Sound power - Sound measurementsSound power or acoustic power P ac is a measure of sonic energy E per time t unit.Preamble: I, like many of our members, am also a member of other allied groups.
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