Acoustics Measurement Sound Reproduction

 In Room Acoustic Measurement

SOUND REPRODUCTION ROOM ACOUSTIC MEASUREMENT

Measurement Objectives of Acoustic Space

Sound Reproduction room is a room that is used to play back the recording. Examples room sound reproduction are: Space hear Audiophile, Control Room in the Recording Studio, Home Theater and others – others.
Acoustic characteristics of a good room is that both sound reproduction room is the room with natural acoustic characteristics. The definition of natural means the sound reproduction that is playing in the room should sound exactly like the master recordings, which means the room does not give extra spice.

The room sound reproduction with excellent acoustic characteristics will produce sound reproduction with accurate tonal balance and displays a holographic sound image.
Measurements objective of room acoustics sound reproduction is to determine the acoustic characteristics of the room sound reproduction. Objective acoustic measurements to determine if the room has been designed and constructed.
Acoustic parameters are measured in the reproduction room are: Room Response and Reverberation Time.

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Image 1. Measurement Setup Photo

Room Response

Room Response is a response frequency measurement results in a point. Frequency response characteristics at the measurement point is a characteristic sound that comes from the direct sound and the acoustic characteristics of the room. Room Response indoor sound reproduction is influenced by Room Modes, Speaker Boundary Interference Response, Reflection and Reverberation.
Here are a few to see room response measurement results on the room sound reproduction.
Gambar 2. Impulse Response (time-level)

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Image 3. Impulse Response Smoothed 1/12 (frequency-level)

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Image 4. Impulse Response Smoothed 1/3 (frequency-level)

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Image 5. Waterfall 2 L efr (frequency-level-time)

Reverberation Time

Room absorb sound energy with an absorption rate of different – different in the frequency range 20 – 20,000 Hz. It makes every room has a unique characteristic reverberation. For example, if a room with a long reverberation at high frequency but shorter at low frequencies, the room can be described as a room with sound character “thin” or “harsh”.
Reverberation theory is introduced by Sabine commonly used to determine the characteristics of the reverberation room. The formula is based on the assumption Reverberation Time reflectance distribution at the room evenly with reflections from all directions. The results of the measurement or calculation of the amount of Reverberation Time is displayed with Reverberation Time (sec) and the amount of frequency (Hz). Reverberation Time graph is usually used to analyze characteristics of the reverberation room.
Room modes provide special difficulties when we want to determine the characteristic reverberation of a small room with a method of measurement. So if we do Reverberation Time measurements in a small room at frequencies below 300 Hz, the most likely is measured decay of room modes. Design of acoustic space is relatively small when using the measurement data or calculations Reverberation Time at frequencies below 300 Hz can cause analytical errors.

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Image 6. Reverberation Time

Measurement Analysis of Acoustic Space

From the results of measurements of the acoustic characteristics of the sound reproduction space followed by two phases of work Analysis of Acoustic Characteristics of the room. From the analysis results can be known if the room already has the characteristics of excellent, good or not good enough. In addition, from the measurement results can be known design factors that can improve the quality of the acoustics in the room.

References:
Everest, F. Alton and Ken C. Pohlmann. Handbook of Acoustics. 1981.
Cox, Trevor. Acoustics Absorbers and Diffusers. 2009

 

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