The Larson Davis SoundTrack LxT® Sound Level Meter Kit KLxT-QPR was specifically designed for gunfire testing, including suppressor and silencer testing. In product testing, the examiner is
often tasked with determining whether the installation of a suppressor results in a “perceptible reduction” in the sound pressure level of a gunshot. The KLxT-QPR is an ideal tool for gathering, analyzing, and presenting detailed
firearm noise data quickly, easily, and concisely. With a sleek ergonomic design, it is able to be held and operated with just one hand. See the following video for a demonstration of a firearms acoustic test.
With the included ¼” prepolarized pressure microphone, Model KLxT-QPR, is capable of reading the very high levels typically associated with gunfire testing. These readings can quickly be organized and stored on internal memory and exported
to a PC for archiving and reporting. Reports generated include selectable noise parameters (peak, background level, max SPL, etc.) as well as calibration history of the instrument, important for courtroom presentations.
All sound level meter rentals include NIST-traceable calibration certificates. Rentals ship with a customer specific expected return date in mind. For example, if equipment is expected to be out for 5 months, the last calibration date will be within
the past 7 months.
Model KLxT-QPR Hardware Features
- Type 1 (Class 1) accuracy for courtroom traceability
- Easy, one-handed operation and large, backlit LCD display
- Simple setup specific to gunfire testing applications
- Over 100dB Dynamic Range (38 - 140dBA in standard range)
- RMS and Peak A, C and Z frequency weighting with slow, fast, and impulse detection
- Microphone extension cabling supported to 60m/200ft
- Over 16 hours of operation using 4 AA batteries included (30 hours with Lithium batteries not included)
Basic Setup for Firearms Acoustic Testing
Download a meter setup file for firearms testing. Download
includes setup files for meters with and without ENV firmware. Please use the file appropriate for your meter. To download and extract the files:
- Click the above link
- At the bottom left of your browser window, you will see LxT-QPR-Setup-Files.zip. RIGHT click on this and choose "Show in Folder"
- The downloads folder will open, and the file LxT-QPR-Setup-Files.zip will be highlighted. RIGHT click on LxT-QPR-Setup-Files.zip and select "Extract All"
- Open the file MD-0445-revNR LxT QPR Setup File Import Instructions.pdf for further instructions
Larson Davis KLxT-QPR User Guide and Hints
There are three options for setting up the LxT meter for Firearms Testing:
- A) Import a setup file via G4 (a setup file for a meter with ENV firmware is linked above)
- B) Setup via G4 software ( view a pdf that details this process for
a meter WITHOUT ENV firmware)
- C) Setup on the meter itself
- Press the middle “soft key” near the screen to select “Menu”
- Hit “Enter” (center of circle keypad area) to select Settings
- Then the left and right softkeys are used to navigate the menu structure
- Navigate to the SLM tab
- Set Peak Weighting to Z. This is the relevant setting for firearm testing. Everything else can stay as-is.
- Navigate to the Control tab
- Set Run Mode to Timed Stop
- Set Time to 5s
- If you have ENV firmware, Measurement History is available
- Turn on Measurement History (This will save all data from your measurement into a single file)
- Press the “Close” soft key in the center near the screen to save your Settings modifications. When asked to “Apply Changes?”, make sure you select “Yes” and press “Enter”.
Physical Setup of Meter and Firearm
To set up the meter's physical location, below are some suggestions. In general, US Military standard testing procedure for sound suppressors consists of:
- The meter should be placed one meter away from and 90-degrees to the side of the firearm’s muzzle
- The meter should be held parallel above the ground at a height of 1.6 meters over a non-reflecting surface
- The muzzle is positioned perpendicular to the microphone before each shot
- Ten non-suppressed readings are taken first and then averaged to provide a baseline figure
- Ten sound-suppressed readings with 3 to 5 minute cooling intervals between each shot are taken
- This data is also averaged and the result subtracted from the baseline figure. This figure represents the degree of sound suppression.
Running the Test
- Press the RUN/PAUSE key to start a measurement with any configuration (different firearm, different suppressor, etc.)
- The arrow in the top right will “run” indicating you are good to measure
- Fire away, making sure to space triggers apart
- If desired, pause the measurement between each shot by pressing the RUN/PAUSE key
- Once 10 good shots have been measured, press the STOP/STORE key. Once pressed, the top right will show a filled in square indicating data is stored.
- Press the STOP/STORE key again to save the data. It will be given a sequential number, something like “LxT_Data.003”. The “003” or whatever number, keep a log handy to correlate this back to what combination of items were tested.
- Once a new firearm/suppressor configuration is ready, press RUN/PAUSE to initiate a new set of measurements
- “LZpeak” is typically the main measurement of interest and is selected in the setups linked above. Please note: if measuring to the current MIL-STD-1474D standard, “LApeak” should be used instead. Much technical discussion
has taken place since the MIL standard has been put in place in 1997, but it has not been updated or replaced yet. Please read the “Firearm Sound Suppression” presentation for more details.
Additional Considerations
Other factors to note during recording may include:
- The ambient temperature
- Humidity
- Barometric pressure
- Elevation above sea level
- Date of test
It is important to note that there will always be minor day-to-day variations in the data obtained as a consequence of changes in the weather parameters.
