Acoustic measurement services

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Key category areas

  • Sound measurement of room space.
  • Calculation on mitigation / improvement of soundscape*.
  • Mitigation of Echo and Noise – modification measures to room interior.

*) Soundscape: components of the acoustic environment. Measured, and perceived.

Areas of interest – in terms of acoustical measurements

A number of areas are of firsthand necessity to process, when taking the journey to control the sound in an interior space.

1. Nature of the room

How soundwaves behave, across the whole frequency range. The frequency-range hearable to humans (20 Hz – 20 kHz). The nature of the behavior is checked by performing Pink Noise testing.

2. Echo

First-time reflections are highest in energy, and therefore should be targeted first to be controlled.

3. Reflections, RT60

Long reflections – a ringing echo, reverberation – is the most disturbing. After countering the first time echo, the second reflection surfaces are next in turn to be controlled.

Reverberation time (T60), is the most fundamental room acoustic parameter. T60 is the time interval where the sound pressure drops to a value of 10−3 (1/1000) of its initial value. In practice, the time definition is the interval during which the sound pressure level decreases by 60 dB. Coined by Wallace C. Sabine (1868 – 1919).

A simple test

You can test the interior behavior of the space where you are, by a strong clap of your hands. If the space is a typical living-room or larger, you may hear an echo. In case a glass vase is present, you may even hear it resonate, the ringing sound fading away.

In an unfurnished apartment you can hear your own voice echo.

Mitigation of Echo, Noise

Mitigation happens by modification of the room surfaces. By taking measures to the interior design. We talk about modification of walls, ceiling, furniture, and other hardware. Also, to enhance weaker sound tones.

  • absorbing or diffusing panels.
  • ventilation vents.
  • your fan-cooled PC.

Standards adhered to, in measurement

  • external microphone, possible to calibrate with a calibrator
  • 20 Hz – 20 kHz frequency range
  • IEC 61672 class 2 frequency response
  • temperature compensated microphone, accurate SPL* monitoring
  • within +/- 1dB compared with professional equipment (class 1**)

*) SPL – Sound Pressure Level
**) Larson-Davis model 831 Type 1 sound level meter

Available parameters

  • A-weighted Equivalent Sound Level (LAeq — A-weighted, equivalent sound level)
  • Maximum Level measured during the a run time (max level)
  • C-weighted Peak Sound Pressure Level (LCpk — C-weighted peak sound level))
  • Total sound dose received during a workday (LAeq.8h, Dose)
  • Time-Weighted Average (TWA)
  • Instantaneous sound pressure level (A, C, or Z weighting)
  • Octave and FFT displayed charts
  • maximum 125 dBspl

In other words, very useful for:

  • Sound power and sound-field analysis
  • Industrial acoustics
  • Near-field response of a studio monitor
  • Room acoustics analysis
  • Sound reinforcement
  • Real-time analysis

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How measurements may look like

Sound pressure levels (SPL), Lp

  • Audible range of human ear goes from 0 dB SPL (hearing threshold)
  • Leaves, fluttering in the distance : 10 dB
  • Leaves, fluttering in the wind : 20 dB
  • A whisper into the ear : 30 dB — a bedroom at night
  • A quiet library : 40 dB
  • Conversation, normal : 60 dB — at 1 m distance
  • A vacuum cleaner, 1 m : 70 dB
  • A diesel truck, 10 m away : 90 dB
  • At a disco, 1 m from speaker : 100 dB
  • A chainsaw, 1 m away : 110 dB
  • Serious discomfort : 120 dB
  • Pain threshold : 130 dB SPL
  • A jet airplane, 50 m away : 140 dB
  • Gunfire usually measure from 160 dB

More reading

You may want to read these scientific studies:

The ASA* Journal of the Acoustical Society of America – Evaluation of smartphone sound measurement applications (apps) using external microphones – A follow-up study – Oct. 2016, Chucri A. Kardous and Peter B. Shaw

NIOSH** Science Blog – So How Accurate Are These Smartphone Sound Measurement Apps? – by Chucri A. Kardous, MS, PE and Peter B. Shaw, Ph.D.

*) ASA – the Acoustical Society of America

**) NIOSH – The National Institute for Occupational Safety and Health (USA), a department under CDC; Centers for Disease Control and Prevention

#RT60 #PinkNoise #echo #reverb