# Intensity and power relationship

### Intensity – The Physics Hypertextbook

Energy, Power, and Intensity. Energy Density. An infinitesimal element of the medium of mass \$dm\$ has kinetic energy in the acoustic limit. Dear P students -- We have not yet talked about sound power, but You may simply want to skip down to the section on Sound Intensity. The terms "force", "work", "distance", "time", "power", "area", and "intensity" all have well-defined meanings within the field of physics, and the.

Instead, amplitude measurements are almost always used as the raw data in some computation. When done by an electronic circuit like the circuits in a telephone that connect to a microphone the resulting value is called intensity.

When done by a neuronal circuit like the circuits in your brain that connect to your ears the resulting sensation is called loudness. The intensity of a sound wave is a combination of its rate and density of energy transfer. It is an objective quantity associated with a wave.

Loudness is a perceptual response to the physical property of intensity. It is a subjective quality associated with a wave and is a bit more complex. As a general rule the larger the amplitude, the greater the intensity, the louder the sound.

## Intensity (physics)

Sound waves with large amplitudes are said to be "loud". Sound waves with small amplitudes are said to be "quiet" or "soft". Today, we'll quantify how loudness depends on the amount of sound energy produced and the distance between the source and our ear Sound Power Sound always has a source. The source could be a musical instrument, people talking, a stereo system or a jet taking off. Different sources produce sounds with different qualities such as pitch and timbre.

### Sound Power and Intensity

What concerns us here is another difference between sources of sound: Sound waves, like other waves, transport energy. For a sound wave, the amount of energy transported is proportional to the square of the amplitude of the wave.

We have indicated this amplitude as p, because it corresponds to the amount of pressure oscillation in the air caused by the sound wave. Where does the sound energy come from? The answer is that some object has converted energy of a different kind into sound energy. Typically, there is some sort of mechanical motion, a vibration of some sort, so mechanical energy is converted into sound energy.

How loud a sound is depends on how rapidly the object converts energy into sound energy. So the relevant physical quantity to relate to loudness is the sound power produced by the source, or the rate at which sound energy is produced versus time. Referring back to our earlier discussions, power is the time rate of change of energy and has units of Joules per second. We give a new name to this unit: It is the lowest value.

Pulse average PA is in between for a given pulse beam. PA and TA are related by the duty factor: If duty factor increases, TA intensity increases. In real-life equipment intensity is not constant within pulses.

Starts out high and decreases towards the end of the pulse. TA averaged over the pulse repetition period. PA averaged over the pulse duration TP no averaging. Putting together spatial and temporal considerations we end up with 6 intensities: Decibels Decibels are used to indicate relative power, intensity, and amplitude levels.