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Sound intensity, also known as acoustic intensity, is defined as the power carried by sound waves per unit area in a direction perpendicular to that area, also called the sound power density and the sound energy flux density. [2] The SI unit of intensity, which includes sound intensity, is the watt per square meter (W/m 2).
The decibel watt (dBW or dB W) is a unit for the measurement of the strength of a signal expressed in decibels relative to one watt.It is used because of its capability to express both very large and very small values of power in a short range of number; e.g., 1 milliwatt = −30 dBW, 1 watt = 0 dBW, 10 watts = 10 dBW, 100 watts = 20 dBW, and 1,000,000 W = 60 dBW.
Sound power or acoustic power is the rate at which sound energy is emitted, reflected, transmitted or received, per unit time. [1] It is defined [2] as "through a surface, the product of the sound pressure, and the component of the particle velocity, at a point on the surface in the direction normal to the surface, integrated over that surface."
For very low-power systems, such as mobile phones, signal strength is usually expressed in dB-microvolts per metre (dBμV/m) or in decibels above a reference level of one milliwatt . In broadcasting terminology, 1 mV/m is 1000 μV/m or 60 dBμ (often written dBu).
where Pd is the power density in watts per square meter (one W/m 2 is equal to 0.1 mW/cm 2), H 2 = the square of the value of the magnetic field in amperes RMS squared per meter squared, E 2 = the square of the value of the electric field in volts RMS squared per meter squared. [6]
Many high-quality domestic speakers have a sensitivity between ~84 dB and ~94 dB, but professional speakers can have a sensitivity between ~90 dB and ~100 dB. An '84 dB' source would require a 400-watt amplifier to produce the same acoustical power (perceived loudness) as a '90 dB' source being driven by a 100-watt amplifier, or a '100 dB ...
geo: average power consumption per person worldwide in 2008 (21,283 kWh/year) 3.3–6.6 × 10 3 W eco: average photosynthetic power output per square kilometer of ocean [23] 3.6 × 10 3 W tech: synchrotron radiation power lost per ring in the Large Hadron Collider at 7000 GeV [6] 10 4: 1–5 × 10 4 W tech: nominal power of clear channel AM [24 ...
The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...