Simple Live Sound Monitoring with Limit Light for NTi’s XL2 Audio and Acoustic Analyzer

December 5 2016, 04:10
The XL2 Audio and Acoustic Analyzer in combination with the new Limit Light visual indicator, from NTi Audio, offer a practical turnkey solution for live sound monitoring. The sound level limits are set in the XL2 and the connected Limit Light provides a pre-warning with an orange light and indicates that actually measured levels have been exceeded with a red light. The dimmable color display provides a simple confirmation of the sound level monitored for the front-of-house engineer and noise control.

NTi’s XL2 Sound Level Meter is the most versatile and ready-to-use solution for level monitoring of live events. Using pre-defined profiles, the device starts measuring immediately after simply switching it on. The new external Limit Light display is clearly visible to the mix engineer. To meet the latest requirements for consideration of bass-heavy performances, the XL2 now also measures the gliding C-weighted average LCeq in 5 seconds to 60 minute intervals as well as the 63 & 125 Hz band levels.

The XL2 Sound Level Meter also provides a complete solution for easy live event monitoring in accordance with different standards. Once powered on, the device automatically starts measuring, providing accurate results every time. In addition to the measurement data, the XL2 simultaneously records the audio signal as a WAV-file. If it is necessary to analyze the data at a later stage, the audio recording supports the process in determining the cause of any potential limit violations.

With the newly available external Limit Light display, the front-of-house engineer gets an inexpensive visualization tool for monitoring the levels during a live event. For convenience, the Limit Light and the XL2 are powered by the same mains adapter. The limit levels are set within the XL2 Sound Level Meter and stored in a profile for re-use.

Since the mixing console is often positioned in a space-limited area, the Limit Light visual indicator was designed so that it can also be operated at some distance from the measuring device. Thus the XL2 can be conveniently placed at a suitable position with the Limit Light mounted via a single XLR cable on the console. To accommodate the variations in background brightness at live events, a rotary dial dims the LED lights to suit even the darkest of environments.

The XL2 Sound Level Meter continuously monitors the low-frequency band levels at 63 and 125 Hz. Additionally, more and more live sound users requested that the XL2 measure the gliding C-weighted average, in order to evaluate the low-frequency sound components at an event via a broad band level. The additional measurement of this moving average level LCeq in intervals of 5 seconds to 60 minutes is now offered by the XL2 Analyzer. In order to determine the level at the loudest point in a fixed venue, the XL2 now also stores the correction values k1 and k2 within the measurement profile. This allows the sound engineer to simply select the pre-defined profile, and be ready for monitoring within a matter of seconds.

NTi Audio Measurement Microphones
NTi Audio develops and manufactures high-quality sound, audio and vibration measurement products. Every new Sound Level Meter is tested prior to shipping to ensure compliance with specification. Measurement Microphones in particular are comprehensively tested in the company’s acoustic measurement chamber.

“Made in Switzerland” is NTi Audio’s stamp of uncompromized quality. This is reflected with diligent quality management. As Markus Frick, Production Manager at NTi Audio explains, “In order to guarantee the highest quality, all instruments are assembled exclusively in-house. During the manufacturing process, our trained team verifies that the individual modules meet or surpass their respective specifications. The finished products are then calibrated according to the IEC 17025 standard.”

Testing a microphone with an acoustic test signal provides a true reflection of the actual purpose of the microphone and ensures accurate free-field frequency response results. Accordingly, this attention to quality is given to every measurement microphone during testing in NTi’s in-house anechoic chamber. The frequency response of every instrument is acoustically determined. The results are required to be even within a narrower tolerance band than is prescribed in the IEC 61672 standard for sound level meters.

“The anechoic acoustic measurement chamber provides us with consistently reproducible measurements. We carry out reference measurements and 100% of our series testing in-house,” Markus Frick proudly reports. The acoustic measurements are performed using a professional microphone test system consisting of the FX100 Audio Analyzer and the Microphone Test Software RT-MicFx. The individual free-field frequency response is recorded and documented with a resolution of 500 points between 20 Hz and 20 kHz. These metrics are available on request to users for all types of microphones.

In a further independent quality check, the acoustic noise floor is determined for each measurement microphone produced. For the certified Class 1 measurement microphones, intrinsic noise is typically 16 dBA. By comparison, the quiet breathing of a human being is about 25 dBA. The ability to measure such low noise levels underlines the sophisticated design of the measurement chamber and its insulation against sound and vibration from outside.

The XL2 Sound Level Meter also provides a programming interface for user-specific noise and quality monitoring requirements. A full command set and sample code is provided. The XL2 measurement data can be queried directly from a PC via the USB interface. A series of queries can be programmed in languages such as C#, Python or LabView. This allows custom measurement applications for sound level monitoring or automated measurements to be programmed on a PC.

From XL2 firmware V3.03, the XL2 Sound Level Meter allows simultaneous external querying of the FFT spectrum, the 1/12 Octave Spectrum and several sound level values. The Remote Measurement Option needs to be installed on the XL2 to enable the remote external queries. Further, installing the Spectral Limits Option provides the high-resolution spectral data.
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