Because RT60 is a measurement of the sound as it decays, it is essential to have sufficient signal to noise. Especially in the 120Hz Octave band, it is common to have excessive levels of noise from the HVAC system. Accordingly, HVAC should be turned off whenever feasible while making the measurements. The quieter it is in the room, the easier it will be to measure the decay, and to get good data. Also, before making RT60 measurements, you should first measure the frequency response of the sound system. If the loudspeakers cannot produce 125Hz, then obviously it will not be possible to make RT60 measurements at 125Hz. Occasionally, sound systems are also unable to produce 8 kHz with the same results. In many cases you will find that in order to suppress feedback, a prior operator has set the EQ so that there is little or no energy to measure in one of the RT octaves. Setting the EQ temporarily back to flat will typically allow the measurement to be made.
MAKING AN RT60 MEASUREMENT WITHOUT A COMPUTER:
Gold Line model DSP30 along with Model PN3B Pink Noise/Tone generator will allow you to make RT60 measurements without the use of your computer. You can capture the measurements to non volatile memory and download to your computer at a later date.
GENERAL RULES WHEN MAKING RT60 MEASUREMENTS WITH A GOLD LINE DSP ANALYZER:
To obtain valid RT60 measurements it is important to suppress, whenever possible, noise caused by heating or air-conditioning systems, fans, or other foreign noise that could interfere with the measurement. Measurements are best taken when traffic noise or activity is at a minimum. Measurements of RT60 require a sound level of at least 21dB ABOVE the AMBIENT SOUND. It is therefore necessary for the triggering sound source to be a minimum of 21dB above the ambient sound at each of the measured frequencies.
USE OF THE PN3B GATED NOISE GENERATOR:
We recommend Gold Line model PN3B gated pink noise/1kHz tone generator as the preferred triggering "GATE" noise source. Switch the PN3B to the "PINK NOISE" position and connect the "GATE OUT" of the DSP Analyzer to the "GATE IN" of the PN3B (the correct cable is provided with the PN3B). The PN3B is powered by a user supplied 9V battery inside of the cover at the base.
Return to DSP options page.