AVIXA CTS-D: Human Perception of Sound (Questions & Answers) Rated 100%

Logarithm - is the exponent of base 10 that equals the value of a number In decibel formulas how should values be logically arranged when comparing two numbers (V1 / V2) - If you expect a gain, place the higher number first. If you expect a loss, place the smaller number first. Explain negative decibel values - measurement just means "less than before," or in this case, "less than the reference level. It does not mean the basic unit it represents has a negative value Decibel - describes a base-ten logarithmic relationship of a power ratio between two numbers. -It uses a logarithmic scale to describe ratios with a very large range of values that can vary over several orders of magnitude. -It is also used for quantifying differences in voltage, distance and sound pressure as they relate to power. Decibels can measure what type of values? - Distance, Power, Pressure, or Voltage Pascal - SI Unit for Pressure Decibel Formula for Power - dB = 10 * log (P1 / Pr) Where: dB = The change in decibels P1 = The new or measured power measurement Pr = The original or reference power measurement if result is positive, the result is an increase, or gain. If it is negative, the result is a decrease, or loss.Decibel Formula for Distance - dB = 20 * log (D1 / D2) Where: dB = The change in decibels D1 = The original or reference distance D2 = The new or measured distance This as the same as: db= 10 * log (D1²/D²) Decibel Formula for Voltage - dB = 20 * log (V1 / Vr) Where: dB = The change in decibels V1 = The new or measured voltage Vr = The original or reference voltage db = 10 * log (V1²/V2²) Reference Level Sound Pressure: 0 dB SPL in Pascals - .00002 Pa / 2x10^-5 Pa / .02 mPa @ 1kHz Reference Level Voltage (Consumer Electronics): 0dBV in Volts - 1 V Reference Level Voltage (pro AV): 0 dBu in Volts - 0.775 VReference Level Power: 0 dBW in Watts - 1W Reference Level Power: 0 dBM in milliwatts - 1 mW / .001W Hearing Damage Threshold in dB - 120 - 140 dB Pro-Audio line level in dBu and volts - +4dBu and 1.23 Volts Consumer Line Level in dBV and milllivolts - -10dBV, 316 mV Threshold of human hearing - 0dB SPL @ 1kHZ, 20micropascals Sound Pressure Level (SPL) - Is a measurement of all the acoustic energy present in an environment. It is typically expressed in decibels. refers to that variation of level above and below ambient atmospheric pressure and is referenced to 20 µPa or 0.0000204 dynes/cm2, the threshold of human hearing. Sound Pressure - refers to the pressure deviation from the ambient atmospheric pressure caused by the vibration of air particles SPL Meter - Gives a single number measurement of the sound pressure at the measurement location. Class 0 SPL Meter - lab reference standard. It has the strictest tolerances and is used when extreme precision is neededClass 1 SPL Meter - is precision measurement. It is useful for taking flat, engineering-grade accuracy measurements instead of wide-range or field measurements Class 2 SPL Meter - is for general purpose. It has the widest tolerances with respect to level linearity and frequency response. Commonly used in AV measurements Class 3 SPL Meter - is intended for noise surveys. It is a simple sound level meter meant to determine if a noise problem exists. If a problem does exist, diagnosing it will require a higher class meter. A-Weighting on SPL Meter - Setting commonly used for environmental, hearing conservation and noise ordinance enforcement. Closely reflects the response of the human ear to noise and its insensitivity to lower frequencies at lower listening levels. C-Weighting on SPL Meter - More uniform response over the entire frequency range. Z-Weighting (0/Flat) on SPL Meter - unweighted setting (no filtering/compensation). SPL Meter: Fast response setting - To capture transient (momentary) levels. SPL Meter: Slow response setting - Similar to how your ears react. For more consistent noise levels or for averaging rapidly changing fluctuations in levels. SPL Meter performance response Standard: IEC - standard relates to frontal incidence correction the microphone have to be oriented directly on axis with the noise source SPL Meter performance response standard: US: ANSI - standard relates to random incidence correction the microphone can be off-axis up to a certain pointWeighting Curve Chart - depicts Frequency (Hz on X) and Gain (in dB on Y) to chart how different frequency response measure by a SPL meter