RU2084840C1 - Device determining time of signal attenuation - Google Patents

Abstract

FIELD: acoustic measurements. SUBSTANCE: device which evaluates time of signal attenuation has controlled generator of testing signal, output amplifier, loudspeaker, acoustic path, microphone, controlled input amplifier, resonance filter, comparator, controlled timer, first register, subtracter, second register, controlled key, control unit, display, level indicator. It performs evaluation of time response of resonance filter to input testing signal. Sequence of line frequency modulated signals of fixed level is used as tasting signal. Presence of reverberation distortions of rooms leads to increased time of signal attenuation and consequently to growth of time intervals measured by controlled timer and to their comparison with standard values. Aids for compensation of systematic error are provided to exclude errors caused by detuning of resonance filter. EFFECT: increased accuracy of measurements. 2 dwg

Description

 The invention relates to the field of architectural acoustics, and in particular to means for acoustic measurements, and can be used to automatically quantify the level of reverberation distortion of premises.

 In a number of applied problems of architectural acoustics, it is required to provide a quick and reliable estimation of the attenuation time (OT) of the acoustic signal of indoor premises. The duration of the time interval during which signal attenuation occurs is one of the most important characteristics that determine a person’s sound perception of acoustic information. Depending on the size of the airspace, speech intelligibility, sound quality of musical works, etc. can vary significantly. Therefore, it is important to create a simple and portable VZ meter, which at the same time would provide the necessary accuracy of the estimates obtained.

 A device for measuring the reverberation time, which contains a noise generator, a third octave filter, an output amplifier, a loudspeaker, a microphone, an input amplifier, a linear detector, an integrating unit, a comparator, a unit for measuring time intervals and an indicator [1], The measurement of the reverberation time in this device is carried out on based on estimating the decay time of the detected averaged level of the received signal to a fixed value. However, the accuracy of this device is very low, due to a significant error in determining the right boundary of the time interval, which determines the duration of the time response to the transmitted acoustic impact.

 A device for measuring the reverberation time of a room is also known, which contains a test signal generator, an output amplifier, a loudspeaker, a measuring microphone, a microphone amplifier, a level meter, two relays, a time delay unit, a start block, an indicator and two keys [2] The operation of this device is based on measuring the signal level before turning off the sound source and after a certain time after turning it off.

 The disadvantage of this device is the low accuracy of the results. This is due to the need to fix low levels of the damped signal, which inevitably leads to significant errors in the presence of acoustic noise in the measured room.

 The aim of the invention is to improve the accuracy of measurements.

 To achieve the goal, a device for estimating the signal attenuation time, comprising a test signal generator, an output amplifier, a loudspeaker, an acoustic path, a microphone, a controlled input amplifier, a controlled key and a display unit, additionally, according to the invention, a resonant filter, a comparator, a controlled timer, are introduced register, subtractor, second register, control unit, level indicator, and the output of the test signal generator through series-connected output amplifier the lighter and loudspeaker are connected to the input of the acoustic path, the output of which through a series-connected microphone and a controlled input amplifier is connected to the level indicator and the input of the resonant filter, the output of the resonant filter is connected to the input of the comparator, and the output of the comparator via a controlled timer is connected to the controlled key, the first output of which connected through the first register to the second input of the subtractor, and the second output of the managed key is directly connected to the first input of the subtractor, the output of the subtractor through the second register is connected to the display unit, the control unit is connected to the control inputs of the managed key and the first and second registers.

 A device for estimating the signal attenuation time (Fig. 1) contains a controlled test signal generator 1, an output amplifier 2, a speaker 3, an acoustic path 4, a microphone 5, a controlled input amplifier 6, a resonance filter 7, a comparator 8, a controlled timer 9, the first register 10, a subtractor 11, a second register 12, a controlled key 13, a control unit 14, a display unit 15, a level indicator 16.

 In FIG. 2 shows timing diagrams explaining the principle of operation of the claimed device.

 In FIG. 2a shows the time dependence of the frequency of the test signal at the output of the test signal generator 1.

 In FIG. 2b shows the voltage diagram at the output of the resonance filter 7 for small values of the signal attenuation time.

 In FIG. 2c shows a plot of the voltages at the output of the resonance filter 7 with a noticeable signal decay time.

 In FIG. 2d shows the time intervals estimated by the controllable timer 9 for the case of a noticeable signal decay time.

 The principle of operation of the inventive device is based on assessing the change in the temporal response of the resonant filter 7 to the reference input test signal. Here, a linear-frequency modulated signal of a fixed level is used as a test signal. The presence of reverberation distortion of the premises leads to an increase in the decay time of the signal, which entails an increase in the time intervals measured by the controlled timer 9, in comparison with the reference values. To eliminate possible errors associated with the tuning of the resonant filter 7, the device provides means to compensate for this systematic error.

 The generator 1 of the test signal generates a periodic measuring signal with a frequency that varies linearly. The central frequency of this sawtooth signal should be selected in the middle part of the audio frequency range, and the frequency rise time (frequency sweep period) is several times (preferably an order of magnitude) longer than the expected room reverberation time. By changing the sweep period, you can change the measurement range of the signal attenuation time.

 The procedure for measuring the delay time of a signal using this device consists of two stages. At the first stage (preparatory), the device is configured. Using the control unit 14, the first and second registers 10, 12 are reset to zero, after which the response time of the resonant filter for the undistorted reverberation signal is measured. To do this, the loudspeaker 3 and the microphone 5 are located in close proximity and, using the control unit 14, the controlled key 13 is transferred to the position at which the signal from the output of the control timer 9 is switched to the first register 10, where the result is stored. At the end of the measurement of the reference response, the controlled key 13 is translated into a position in which the signal from the output of the controlled timer is switched to the subtractor 11. Then, the receiving and transmitting parts of the device are placed in a measured room and the input signal level is adjusted, which is adjusted by adjusting the gain of the controlled input amplifier 6 by Based on the readings of the level indicator 16.

 At the end of the device setup, the measurement procedure begins directly.

 The signal from the output of the test signal generator 1 through the output amplifier 2 and loudspeaker 3 enters the estimated acoustic path 4. At the output of the acoustic path 4, the signal is received by the microphone 5, amplified by a controlled input amplifier 6, and fed to the resonant filter 7 tuned to the average frequency of the test signal.

 In the case of a short decay time, the signal at the output of the resonant filter 7 will have the form shown in figure 2b. Obviously, in this case, the duration of the temporal response of the resonant filter 7 for a fixed scan period of the generator 1 of the test signal will be determined only by the quality factor of the filter, and therefore can be made very small.

 In the case when the acoustic path has significant reverberation distortion, the pulses at the output of the resonant filter 7 expand. Qualitatively, the waveform at the output of the resonant filter 7 for this case is illustrated in figure 2B.

 As a measure of the delay time of the signal, here we use the change in the response time of the resonant filter 7, which is determined using the threshold element of the comparator 8 and is used to start and stop the control timer 9. Then, the constant component of the response is compensated in the subtractor 11. The constant component of the response time corresponds to the conditions under which there is no reverberation of the room in the acoustic path, and its value is estimated and recorded in the manner described above in the device setup mode. The value obtained at the output of the subtractor 11 is read into the second register 12 and stored in it until the next measurement. The measurement result is displayed in the display unit 15.

 The device described above can be very easily implemented as a compact device based on analog-to-digital technology. At the same time, this device will provide the ability to quickly carry out the necessary measurements and guarantees the reliability of the results.

Sources of information
1. Building acoustics analyzez, type 4418, Bruel Kjxr, DK 2850, NaERum, DENMARK.

 2. Reference on acoustics / Iofe V.K. Korolkov V.G. Sapozhkov M.A. M. Communication, 1979, p. 296 297.

Claims (1)

 A device for determining the signal attenuation time, comprising in series a test signal generator, an output amplifier and a speaker acoustically connected to the input of the acoustic path, a controlled input amplifier, a controlled key and a display unit, characterized in that it is equipped with a resonant filter, a comparator and a controlled timer, first register, subtracter, second register, control unit and level indicator, output controlled input gain I am connected to the level indicator and the resonant filter input, the output of the controlled timer is connected to the input of the controlled key, the first output of which is connected through the first register to the second input of the subtractor, and the second output of the controlled key is connected to the first input of the subtractor, the output of the subtractor through the second register is connected to the block display, the control unit is connected to the control inputs of the managed key and the first and second registers.

Images