Suitable Method to Be Applied for Measurements of Reverberation Time - Coursework Example

Acoustic Project Name: Course: Instructor: Institution: Location: Acoustic Project Introduction In physics, the sound is the vibration that propagates as the typically loud mechanical wave of a displacement and the pressure, through the medium for example water or air. In psychology and physiology, the sound is a reception of those waves and how a brain perceives them. According to American National Standard (ANS), 2013 (a) Sound is defined as the oscillation in particle displacement, pressure, particle velocity, stress, etc. that is propagated in the medium with internal energy, for example, viscous or plastic or a superposition of those propagated oscillations. (b) Sound is defined as a loud sensation caused by an oscillation in particle displacement, pressure, particle velocity, stress, etc. that is propagated in the medium with internal energy, for example, viscous or plastic or a superposition of those propagated oscillations. Sound can move via a compressible media like air, solid, and water as the longitudinal waves and moves as the transverse waves in the solid material. The waves of sound are produced by the sound source like a vibrating diaphragm of the stereo speaker. A sound source generates the vibrations in a surrounding medium. As a source goes on with the vibration of the medium, these waves move away from a source at a speed of sound, therefore creating a sound wave. At a fixed length from a source, velocity, pressure, and displacement of a medium change in time. At a particular instant of time, velocity, pressure, and movement change in space. The medium particles do not move with the sound wave. This intuitively is visible for the solid and is valid for the gasses and liquids i.e. particles vibrations in gas or liquid carry the vibrations, whereas the average particles positions over time remain constant. Sound wave is reflected attenuated or refracted by a medium during propagation. When sound wave is moving via the medium that which not have steady physical characteristics, it may get refracted (either focused or dispersed) Mechanical vibrations that can be translated as a sound are capable to move via all kinds of matter: liquid, plasmas, gasses, and solid. The thing that supports a sound is known as a medium. Sound cannot move through the vacuum. At times, there is too much sound that the person can hear that are not wanted, and these sounds are called noises. These noises can at times interfere with normal sleep and majority of other inconveniencing things, and that is why scientist came out with acoustic materials that are called sound insulation. These materials are designed and applied for a purpose of absorbing sound that might otherwise be reflected. Acoustics is a science that the combination of disciplines that deals with a study of the mechanical waves in gasses, liquids, and solids including ultrasound, sound, vibration, and infrasound. Uses of acoustics are common in almost every aspects of a modern society, sub-disciplines include processing, aero-acoustics, bioacoustics, architectural, electro-acoustics, musical acoustics, etc. In acoustic and psychoacoustics, reverberation, is a persistence of the sound after the sound has been produced. The reverberation, or a reverb, is created when the sound or a signal is reflected triggering the massive amount of reflections coming up and decay as a music is taken up by the objects surfaces in a space that could include people and furniture, and air. This is the most noticeable if the source of sound stops but reflections keeps on reducing the amplitude up to zero amplitude. Reverberation is the frequency dependent. The reverberation time or decay length gets a special attention in an architectural spaces design that requires to be given particular reverberation period to attain an optimum performance to meet their intended design activity. Although the large amount of parameters had been defined in the past years so as to explain and evaluate acoustic properties of the particular space, a reverberation time had as a primary indicator of the acoustical behavior. Hence, the extensive research can be done in the attempt to determine a best possible setup of the measurement needed for used in measurements of reverberation time that will give very reliable results. As the part of the research on reverberation time measurements, this report provides the overview of a most used methods applied for this type of measures through comparison of the results got with every method. Over the past years, the numbers of distinct methods for reverberation time measurement have evolved and implemented, these methods are: an interrupted noise, integrated impulse response, method of recording a room response to the impulsive source, a burst method. These methods had been examined, and the outcomes got using them have been compared to choose the best and reliable one for use in the field measurements. To reduce the level of uncertainty, measurements in all were done using a same source of sound, except when using the impulsive source, for example, a balloon. Furthermore, all the responses were noted down with same microphone, but for a burst method receiver was not used. Measurements were observed in two little but acoustically distinct spaces. Methodology Impulse response method was used in this experiment. An integrated impulse response method was developed and implemented in the number of computer users. The application selected to be used in this investigation is an ARTA Software, designed strictly for measurements of impulse response and the parameters obtained from it. The typical test signals in the ARTA for measurements of impulse response are pink swept sine, noise, and MLS and a decision was taken to investigate all test signals to determine the most suitable one to be applied in measurements of reverberation time. Description of the room investigated. The aim of doing this task was to obtain the reverberation time of the sound when the source of the sound was turned off. The measurement was done in the room with various acoustic characteristics. The room has the length of 10.2 m, width of 7.1 m and height of 3.0 m and has the room volume of 217.26 m3.Since all acoustic elements that were used for the acoustic treatment could easily be picked off from a wall and fixed back (concept for the changeable acoustics), that room acts as the constant place for testing different acoustic arrangements. The current set in the room brings to close to the good listening room. A contemporary interior of a room with the source and microphone placed in the suitable arrangement was used. The room serves as the multipurpose space having the primary function to provide better access to several functions. The room is elongated with tight rectangular shaped having the staircase for access to other rooms. The room was chosen due to proximity and availability. In the process of provide an equal and favorable condition for the method chosen which needs the loudspeaker as the source, i.e. an integrated impulse response method. The test signal was the laptop computer that was connected to a power amplifier through the Sound Level Meter having a Reverberation Processor Procedure The size of the room was measured, and the volume of the room was determined. The loudspeaker produced the source and after some time it was turned off and duration of sound to stop altogether was recorded. The interrupted noise method mainly uses a portion of pink noise with a duration of several seconds, which ends abruptly. A response of a room to the signal of noise, i.e. reverberation, was recorded as the wave file and imported into the ARTA for more analysis. The method that uses the impulsive source of a particular type by noting the response of a room to it was similar to an interrupted noise method (Sujatha 18). Unlike the method of noise interruption that uses the loudspeaker, this method permits the wide range of impulsive sources, such as pistol shots, air-filled balloons, hand clap, firecrackers, etc. Detailed description of the software ARTA software is the collection of the programs for the measurements of audio and the analysis in an acoustical and the communication systems. ARTA software applies the standard and the professional sound cards of the PC and the interfaces for an audio signal receiving and generation. ARTA software is comprised of the following programs: ARTA - a program for the measurement of impulse response and analysis of real-time spectrum and measurements of frequency response. STEPS - a program for measurements of frequency response with the excitation of stepped-sine. Simultaneously with the analysis of frequency response, a program determines the levels of the 2nd, 3rd, 4th, 5th and the higher order of harmonic distortions. LIMP - a program used for measurement of the loudspeaker impedance and estimation of speaker parameters. ARTA program performs the following tasks for systems measurement: Generator signal for the following signals: pink noise, white noise, periodic pink noise, periodic white noise, sine, two sine, speech signal, multitone, square, and triangle. Measurement of Impulse response systems, Dual and Single channel Fourier analyzer Spectrum, THD analyzer and octave band and Triggered storage scope. With the calibrated microphone, ARTA is used as the virtual IEC class 1 SPL meter together with the real time mode: ARTA program is applied in the following analysis: Gated response of the frequency, Smoothed response of the frequency (in 1/n-octave bands), Step response, The envelope of the impulse response (ETC – curve) Burst decay waterfall graphs and sonogram. Energy decay prevalent in reverberant environments Acoustic parameters of the room Results and discussion For yielding the good results of reverberation time measurements in the efficient manner, all data obtained during an analysis process were analyzed with the ARTA software. An integrated method of impulse response implemented in an ARTA permits a direct data analysis obtained. Although the standard practice needs measurements of reverberation, time to be done in the octave frequency bands including the center frequencies ranging from 125 Hz - 4 kHz. A decision was taken to extend a frequency range of choice to octave bands having the center frequencies ranging from 63 Hz and 8 kHz so as to address all problems in the proper manner. An interrupted noise method give the dynamic range that is narrow as compared to other methods used in earlier (Rossing 32). The loudspeakers that are fed with the sine-like signal provide the sound pressure that is the few decibels high than the one that they could give when fed with the noise-like signal of the same amplitude. In addition, when an averaging process is used in measuring an integrated impulse response it gives the less marginal decibels in a useful dynamic range. Energy decay recorded in the room at various microphone positions for integrated impulse response (IIR) method applied in the ARTA using a pink noise and swept sine signals and implementing asynchronous mean so as to increase a dynamic range. Conclusion The primary aim of doing papers paper was to determine a suitable method to be applied for measurements of reverberation time. The results indicate that the method of integrated impulse response using a swept sine signal gives a better outcomes, given the same measurement, since in these situation it was in a position provide a wider dynamic range. Though reverberation time is never recommended to be measured by recording the room response to the excitation with an impulsive source because of no repeatability of that kind of measurements, we have discovered that this method is suitable since the results are normally in good agreement with those outcomes obtained using other methods (Fahy 24). Suggestions for future improvement In the measurement of reverberation time, the room should be free from echo because repetition gives the reflected feedback that interferes with normal sound. Reverberation time should not be recorded together with the room response because response of the room provides inaccurate results. References Fahy, F., & Gardonio, P. 2007. Sound and structural vibration radiation, transmission and response. Amsterdam, Elsevier/Academic. http://www.books24x7.com/marc.asp?bookid=28067. Rossing, T. D. (2014). Springer handbook of acoustics: with ... 90 tables. New York, NY [u.a.], Springer Sujatha, C. (2010). Vibration and acoustics: measurement and signal analysis. New Delhi, Tata McGraw Hill Education Private Ltd. Read More

The thing that supports a sound is known as a medium. Sound cannot move through the vacuum. At times, there is too much sound that the person can hear that are not wanted, and these sounds are called noises. These noises can at times interfere with normal sleep and majority of other inconveniencing things, and that is why scientist came out with acoustic materials that are called sound insulation. These materials are designed and applied for a purpose of absorbing sound that might otherwise be reflected.

Acoustics is a science that the combination of disciplines that deals with a study of the mechanical waves in gasses, liquids, and solids including ultrasound, sound, vibration, and infrasound. Uses of acoustics are common in almost every aspects of a modern society, sub-disciplines include processing, aero-acoustics, bioacoustics, architectural, electro-acoustics, musical acoustics, etc. In acoustic and psychoacoustics, reverberation, is a persistence of the sound after the sound has been produced.

The reverberation, or a reverb, is created when the sound or a signal is reflected triggering the massive amount of reflections coming up and decay as a music is taken up by the objects surfaces in a space that could include people and furniture, and air. This is the most noticeable if the source of sound stops but reflections keeps on reducing the amplitude up to zero amplitude. Reverberation is the frequency dependent. The reverberation time or decay length gets a special attention in an architectural spaces design that requires to be given particular reverberation period to attain an optimum performance to meet their intended design activity.

Although the large amount of parameters had been defined in the past years so as to explain and evaluate acoustic properties of the particular space, a reverberation time had as a primary indicator of the acoustical behavior. Hence, the extensive research can be done in the attempt to determine a best possible setup of the measurement needed for used in measurements of reverberation time that will give very reliable results. As the part of the research on reverberation time measurements, this report provides the overview of a most used methods applied for this type of measures through comparison of the results got with every method.

Over the past years, the numbers of distinct methods for reverberation time measurement have evolved and implemented, these methods are: an interrupted noise, integrated impulse response, method of recording a room response to the impulsive source, a burst method. These methods had been examined, and the outcomes got using them have been compared to choose the best and reliable one for use in the field measurements. To reduce the level of uncertainty, measurements in all were done using a same source of sound, except when using the impulsive source, for example, a balloon.

Furthermore, all the responses were noted down with same microphone, but for a burst method receiver was not used. Measurements were observed in two little but acoustically distinct spaces. Methodology Impulse response method was used in this experiment. An integrated impulse response method was developed and implemented in the number of computer users. The application selected to be used in this investigation is an ARTA Software, designed strictly for measurements of impulse response and the parameters obtained from it.

The typical test signals in the ARTA for measurements of impulse response are pink swept sine, noise, and MLS and a decision was taken to investigate all test signals to determine the most suitable one to be applied in measurements of reverberation time. Description of the room investigated. The aim of doing this task was to obtain the reverberation time of the sound when the source of the sound was turned off. The measurement was done in the room with various acoustic characteristics. The room has the length of 10.

2 m, width of 7.1 m and height of 3.0 m and has the room volume of 217.26 m3.

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