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1
Content available Effect of highpass filtering on the speech transmission index
Dziechciński Paweł
Vibrations in Physical Systems
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2022
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Vol. 33, nr 3
art. no. 2022306
EN
Highpass filters are commonly used in the signal chain of public address systems. One of the reasons for using a highpass filter is to protect the loudspeaker from unwanted low-frequency signals. In addition, it can increase the intelligibility of speech. In this paper, the effect of the cutoff frequency and order of a highpass filter on the speech transmission index, the crest factor, and the sound level are presented. Analyses were performed for an ideal transmission channel, taking into account reverberation time, interfering noise, and high levels of sound. A computer model of the public address system developed by the author, based on the direct STIPA method, was used. This model enables analyses in the nonlinear range of power amplifier operation, which is often used in public address systems but is not considered in commercially available simulation programs.
2
Content available Effect of Power Amplifier Distortion on the Speech Transmission Index for Public Address Systems
Dziechciński Paweł
Archives of Acoustics
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2022
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Vol. 47, No. 2
191--199
EN
The effect of the power amplifier on speech intelligibility in public address systems is often marginalised – i.e. it is assumed that it does not introduce significant signal distortion. This approach is justified when the linear range of the amplifier is used. The large crest factor of the speech signal and economic considerations mean that the amplifier also works in the non-linear range. In this paper, the effect of power amplifier distortion on the speech transmission index for public address systems (STIPA) is presented. In the first step, this influence was evaluated by measurements for Class AB and D amplifiers. Then, a computer model of the public address system based on the direct STIPA method, taking into account the non-linear properties of the amplifier, was proposed. Using the computer model, the optimum amplifier driving values were determined taking into account the reverberation time and interfering noise.speech transmission index; power amplifier; public address system.
3
Content available A computer model for calculating the speech transmission index using the direct STIPA method
Dziechciński Paweł
Vibrations in Physical Systems
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2019
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Vol. 30, nr 1
art. no. 2019129
EN
Computer models currently used for the simulation of the speech transmission index (STI) calculate the STI using the statistical method or are based on numerically determined impulse response of the transmission channel. The limitation of both these computational methods is that they do not allow to take into account the nonlinear properties of the transmission channel and fluctuating background noise. This paper presents a proposition of a model based on the direct STIPA method. This model allows computer simulations of STIPA for distributed sound systems, and enables analysis to include both changes in signal dynamics and fluctuating background noise. The paper presents the idea of the model and validation of its basic elements - the generator and the analyser. The possibilities of using the model for computer simulation of outdoor public address systems were also discussed.
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