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Terminología de Acústica Acústica
Aquí podrá encontrar algunas de las principales definiciones de acústica. (Texto en Ingles.)
Acoustics - the science of sound, how it travels and how one can predict and control its behavior.
Ambient Noise - the sound energy assoc-iated with a given environment, being usually a composite of those sounds which are fundamentally related to the environment itself. This term can take on a variety of meanings, depending on the definition of the environment.
Amplitude - the amount by which the absolute pressure is varied from its static value by the presence of the sound wave. Generally measured in units of pressure, such as pounds per square inch, newtons per square meter, etc. and expressed in a logarithmic fashion when compared to a reference pressure in "decibels".
Audiometric Enclosure - an environment in which one can make reliable measure-ments of the effectiveness of one's ability to detect and understand certain types of sounds.
Broadband Noise - a noise having a frequency content such that sound energy is present at many frequencies within the human hearing range.
Conditioned Operant Response (COR) Systems - A measurement system allowing a trained professional to evaluate the ability of a patient to hear an acoustic stimulus when the patient cannot provide the examiner with a standard response. COR systems usually involve a system which provides a visual or other non-acoustic stimulus accompanying the auditory stimulus and the patient is "conditioned" to respond to the visual stimulus whenever the audible stimulus is detected.
Cycle - a complete oscillation of instantaneous pressure above and below the ambient static pressure at a given frequency.
Decibel (dB) - the fundamental unit in which sound pressure levels are expressed. The SPL (sound pressure level) in decibels represent the logarithmic value of the instantaneous pressure compared to a reference pressure. (See Appendix)
Frequency - the number of complete cycles above and below the static pressure, per second, caused by a sound wave. Expressed in units of hertz (Hz), with one hertz being one cycle per second.
Harmonics - tones, in addition to the fundamental frequency, which are integral multiples of the fundamental frequency.
Insertion Loss (IL) - the reduction in noise brought about by the introduction of an acoustical element into a given environment.
Narrowband Noise - having frequency components covering a small portion of the range of human hearing, generally less than one-third octave.
Natural Frequency - the frequency at which a mass resting on a spring would tend to "naturally" vibrate. This frequency is related to the weight of the object resting on the spring and the stiffness of the spring.
This term is generally used to describe the
effectiveness of an isolation system used to isolate an acoustical enclosure from vibrations in the host facility. A lower natural frequency would provide more effective vibration isolation of the enclosure at a given frequency, with the tradeoff being a less stiff or "softer" isolation system.
Noise - sounds, generally classified as undesirable.
Noise Dose - a measure of an individual's noise exposure relative to a level expected to cause significant cumulative hearing damage (denoted by 100% noise dose). e.g. 90 dBA (A-weighted db) for 8 hours = 100% noise dose.
Noise Isolation Class (NIC) - a single number rating of the noise reduction properties of an enclosure. Noise isolation class ratings are generated by conducting an ASTM E-596 noise reduction test and analyzing the data in accordance with ASTM E-413.
Noise Reduction (NR) - a measure of the amount by which the exterior airborne sound pressure level, is reduced inside an enclosure. Noise Reduction is measured in a reverb-eration chamber using the procedures of ASTM E 596, and expressed in decibels as a function of frequency.
Noise Reduction Coefficient (NRC) - a single number rating of an absorber based on its average absorption coefficients in the 250, 500, 1000, and 2000 Hz one-third octave bands.
Octave - interval between two frequencies whose ratio is a factor of two. For example,
sounds with frequencies 1000 and 2000 Hz are said to be one octave apart.
Octave Band - a range of frequencies lying one-half octave on either side of a given center frequency. The ANSI standard octave band center frequencies around which most standard acoustical measure-ments are made are 63, 125, 250, 500, 1000, 2000, 4000 and 8000 Hz.
Pure Tone - a sound that has all of its energy concentrated at a single frequency.
Reverberation - the persistence of sound in an enclosed space because of multiple reflections of the sound energy from the boundaries of the space until it is absorbed by some material within that space.
Reverberation Room - a room whose walls are designed so as to absorb as little acoustical energy as possible. The sound in such a room approximates a diffuse field, in which the sound energy is evenly distributed throughout the room and travels with equal probability in all directions. Such rooms provide a useful environment for the measurement of acoustical properties such as noise reduction of acoustical enclosures, transmission loss or enclosure components, and the sound absorptive properties of the surface of a material.
Reverberation Time - the time required for a sound to decrease its level by 60 dB when propagating within the boundaries of an enclosed space. (See Appendix)
Root-Mean-Square (RMS) - positive value quantity of sound pressure which is the result of the instantaneous pressure being squared, averaged, and square-rooted.
Sabin - a unit of sound absorption having the dimensions of square feet.
Sound - An audible pressure disturbance in a medium, in this case, air.
Sound Absorption - the property possessed by a material which describes a material's ability to remove energy from a sound field, usually by converting sound energy to heat.
Sound Absorption Coefficient - the decimal ratio of the sound absorption footprint of a material to its plan area.
Sound Field Measurements - audiometric measurements that are made in an open sound field situation, utilizing speaker systems and patients with their ears open, without the use of headphones.
Sound Power Level - the amount of acoustical energy that is generated by a sound source per second. Sound Power is a fundamental measurement of the energy emitted by an object, whereas Sound Pressure is a result of both the sound power of a source and the effect of the environment on the propagation of that source's energy within the space.
Sound Pressure - the instantaneous pressure that is generated at a point, above or below the static pressure at that point, by a sound wave.
Sound Pressure Level (SPL) - is 20 times the logarithm to the base 10 of the ratio of the pressure generated by a sound to a reference pressure, expressed as decibels (dB). Sound pressure levels of particular interest are those levels to which the human hearing mechanism responds effectively, being values from 0 dB to 120 dB. (See Appendix)
Sound Transmission Class (STC) - a single number rating of the transmission loss properties of a material, which provides an
"average" rating of the effectiveness of the material against speech frequencies.
Sound Transmission Coefficient - the fraction of incident sound transmitted through a material or component.
Sound Transmission Loss (STL) - the decibel difference between the sound energy incident on a material and that penetrating through the material. Sound Transmission Loss is measured in accordance with ASTM E 90.
Spectrum - is a description of a sound's resolution into frequency components or frequency bands. The frequency and amplitude content of a sound or noise.
Standing Waves - sound energy trapped between two or more reflective surfaces, which generate regularly patterned pressure distributions in the space.
Third Octave Band - a range of frequencies lying one-sixth octave on either side of a given center frequency. The standard 1/3 Octave Band center frequencies are 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300, and 8000 Hz.
Tone - sound at a single frequency.
Wave - a disturbance traveling in a medium.
Wavelength - the physical length of one cycle of a wave in a given medium.
Weighting Networks - used in conjunction with sound level meters and other sound measuring instruments. Electronic circuits used to filter the input of a microphone signal to emphasize or de-emphasize sound energy in certain frequency bands prior to the calculation of a single number frequency weighted average sound pressure level. Express in decibels (dB). The two most popular types of weighting networks are :
A Weighting : A weighting network that emphasizes sound energy in the bands above 500 Hz and below 8000 Hz and de-emphasizes sound energy in the bands below 500 Hz. This weighting scheme characterizes a noise in a manner that gives a measure of how the noise can be expected to damage the human hearing mechanism.
C Weighting : A weighting network that emphasizes sound energy between the frequency ranges of 20 Hz and 20,000 Hz and de-emphasizes energy below 20 Hz or above 20,000 Hz. This weighting scheme characterizes a noise in a manner that give a measure of the total sound energy that is contained within the human hearing range.
