Professional Definition

The sound intensity level is a logarithmic measure of sound intensity, expressed in decibels [dB]. It is a quantity determined by the formula: LI = 10 log (I / I0), where 'I' is the measured sound intensity [W/m2], and 'I0' is the reference intensity equal to 10 to the power of -12 W/m2.

Unlike acoustic pressure, sound intensity is a vector quantity – it possesses not only a value but also a direction and a flow of energy. The sound intensity level informs us about the stream of acoustic energy flowing through a unit area perpendicular to the direction of the wave propagation, scaled to a convenient logarithmic form.

Acoustics in Simple Words

This can be compared to a stream of water from a garden hose hitting a wall. Pressure is the force with which the water pushes against the surface at a given point. In contrast, intensity is the amount of water (energy) that actually flows through a given frame (e.g., 1 meter by 1 meter) in one second. The sound intensity level is simply recording that amount of flowing “water” on a decibel scale, which makes it easier for us to assess whether we are dealing with a gentle drizzle (silence) or a powerful waterfall (noise).

Summary

The sound intensity level is a key parameter in advanced noise diagnostics, allowing for the determination of the direction of acoustic energy flow. It is determined from a logarithmic formula in relation to the threshold of hearing and expressed in decibels.