Noise Locator NL1

Know where noise comes from – with confidence.

The NL1 Noise Locator is a 3D outdoor sound intensity sensor that adds directional intelligence to noise monitoring systems.

Conveniently attached directly below the measurement microphone, and connected to an XL3 Sound Level Meter, it identifies the Direction Of Arrival (DOA) of the dominant noise source.

This compact sensor provides noise directivity in environmental monitoring where you are concerned with noise from a defined direction.

Determine direction of dominant noise
Easy to pinpoint the sound source
Compact and outdoor-ready design
One-cable XL3 integration
Reliability indicator (ΔPI) adds a level of confidence to the result

Why NL1

A compact solution
Especially effective for low-frequency analysis
Simple inline integration between XL3 and microphone
Designed for permanent outdoor operation
Synchronized logging of sound levels and direction
Pressure-Intensity Indicator (ΔPI) shows confidence level
Reports horizontal and vertical Direction Of Arrival
(azimuth and elevation)

Typical Use Cases

The NL1 is mounted below an M2340 microphone enclosed in a WP40 weather protection case and bird spike.

Applications include:

Environmental noise monitoring
Construction, road, aircraft and rail noise investigations
Industrial noise monitoring where there are multiple sources

Trustworthy Results

Real-world sound measurements are often affected by reflections and multiple sound sources. To help you judge the reliability of each result, every NL1 measurement includes a Pressure-Intensity Indicator (ΔPI).

ΔPI shows how trustworthy the sound direction result is. Lower values mean higher confidence, while higher values indicate that reflections or other sound sources may be influencing the measurement.

When the sound field is clean and well defined, ΔPI is close to zero and the result can be trusted. As reflections or additional sources increase, ΔPI rises, signalling reduced confidence.

Only measurements that meet the ΔPI criterion are used for directional analysis. This allows automatic filtering and defensible, reliable results in post-processing.

How it Works

The NL1 uses eight microphones arranged in a compact 3D geometry. From these, 12 sound intensity probes are formed with a spacer of 2 cm, allowing A-weighted resolution in octave bands from 63 Hz to 4 kHz.

Sound intensity describes the direction of acoustic energy flow. By evaluating the resulting intensity vectors, the NL1 determines:

Azimuth (horizontal direction, referenced to North) and

Elevation (vertical angle, referenced to the horizontal)

Installation Guidance

For best results:

Avoid nearby reflective surfaces (recommended distance ≥ 5 m)
Install at sufficient height to reduce ground reflections
Position the sensor between relevant sources where possible

XL3 Integration

The NL1 connects directly to the XL3 Sound Level Meter via a single USB cable:
- Power and data over one cable
- Direction data synchronized with noise data logging
- Real time data available via the XL3 Streaming API

Monitoring Software

MeasurEye – segment-based accumulation of noise by source direction

MeasurEye

Reporting Software

Data Explorer – automatic marker generation based on directional segments

Analysis Software

NL1 Lab – experimental analysis tool demonstrating NL1 capabilities

NL1 Lab

Key Technical Data

Frequency range: 63 Hz – 4 kHz (octave bands)
Time resolution: 100 ms or 1 s
Dynamic range: 25 dBA – 125 dBA
Power consumption: < 1 W (powered via USB)
Based on sound intensity, rather than beamforming or pressure arrays
Outdoor design, high wind and weather resistance
The Pressure–Intensity Indicator (ΔPI) shows how reliable the sound direction result is by comparing sound pressure and sound intensity. A small value means the result is trustworthy, while a larger value indicates lower confidence.

Trusted by professionals worldwide.

As a research laboratory invested in supporting communities through real time noise monitoring, I am very happy to exclusively use NTi instruments. Not only are the robust, easy to use, and provide high quality data, the customer service is outstanding and their team will work with you to find the most cost effective and appropriate solutions needed for problems ranging from easy to difficult.

Erica D. Walker MSc, ScD, RGSS Assistant Professor of Epidemiology, Brown University School of Public Health

I’ve been using the XL2 for over 15 years for short-term and long-term measurements in all kinds of indoor and outdoor environments all across the country. The meter gets me what I want, when I need it. It’s not only the best value for acoustical measurements, it’s the best tool period. I bet my company and reputation on XL2 results and it has not let me down. You would be crazy not to consider adding NTi instruments to your toolkit.

Herb Singleton, P.E., INCE Bd. Cert., President, Cross-Spectrum Acoustics

We at Constructure GmbH use two XL3 sound level meters for noise monitoring during demolition work. We are very satisfied with these highly user-friendly instruments, the online monitoring in the MeasurEye Cloud, the good advice and qualified support. Factory calibrations at NTi Audio are also handled very smoothly and without complications.

Markus Rost, Managing Director, Constructure GmbH