Sound

670 Words2 Pages

Sound

Decibels are the units of measurement used to describe voltage and power levels. The abbreviation for a decibel is dB (Sauvala). Some decibel comparisons are: 10 dB is about as loud as someone whispering, 70 dB is a shouted conversation, and 110 dB is as loud as a jet engine ("Sound"). Decibels are the expressions of ratios. Some formulas for decibels are power =10log(P1/P2)(P1= power 1 and P2= power 2) and voltage =20log(v2/v1)(V2= voltage 2, V1= voltage 2) (jgoldste@wyoming.com). Decibels are measured by 6's. For example, 6 dB is twice the original value (0 dB) and -6dB is ½ of the original value (0 dB) (Sauvala). O dB is the minimum a human can hear and 140 dB is the threshold of pain for a human (Freedom). Decibel means the measurement is a ratio measured on a logarithmic scale and whenever you add 6 dB the voltage doubles (BBC Online). The average human ear cannot notice decibel changes of less than one decibel (malcolm@mcs.net). Every time the distance from a sound source doubles, there is a drop of 6 dB and the formula for this is DC= 20log(distance1/distance2) (DC= decibels of change). You round decibels to the ones place (Mc Squared System Design Group).

There is only one decibel system, but there are two ways to express values--power decibels and voltage decibels. Power decibels are used to express sound pressure levels and power amp and speaker specifications. They are used for equipment that translates signals back to sound and to someone's ears for hearing. Voltage decibels are used to express gain, loss, levels, noise, and line equipment specifications. These are used in most equipment that pick up sounds, converts them to electrical signals and sends them from one point to another. Both of these can be converted to each other. If you have power dB all you have to do is double it to get voltage dB and if you have voltage dB than you take half of that for power dB (malcolm@mcs.net).

Sound has three measurable parts: frequency, amplitude, and duration. Frequency is the rate of vibration that determines how high or low the pitch is. "Amplitude is the magnitude of the vibration, which determines how loud the sound is."(Freedom) Duration is how long the sound lasts, measured in seconds.

Open Document