Measurement History and Event Detection in Noise Monitoring

While Time Histories are typically logged at one sample per second, longer-term averages are often useful to see trends, e.g., 10 minute or hourly averages. 831C-ELA firmware enables Measurement History (MH) and logs these parameters similar to Time History (TH) over a longer interval time. MH and TH can run together simultaneously or independently. Data for each measurement or location is saved in a unique MH record and may include the Leq, Lmax, Lmin, SPL, and statistical distribution of the SPL (Ln). A complete set of MH records then can be stored in a single measurement that keeps all the noise survey data in a single file. Finally, an automated sound recording at the beginning of each MH period can be achieved with 831C-SR firmware.

Measurement History

When the SoundAdvisor™ Sound Level Meter Model 831C is set to MANUAL RUN mode, Measurement History can be used to construct a noise survey. Data for each measurement or location is saved in an individual file and may include the Leq, maximum and minimum SPL and statistical distribution of the SPL (Ln).

Measurement History records are available for easy review on SoundAdvisor. The current measurement is visible on the “Current” display tab, while completed measurements can be browsed in the “Measurement” tab. When combined with 831C-LOG, the time history detail of each measurement can be viewed quickly using keypad shortcuts. Finally, an automated sound recording at the beginning of each measurement can be achieved with 831C-SR firmware.

Automatic Event Detection and Event History

In the SoundAdvisor Sound Level Meter Model 831C, events are defined as either:

• Exceedance of a fixed threshold level for a minimum duration
• Exceedance of a dynamic threshold level for a minimum duration
• External trigger set by the digital input signal
  

Event Definition on SoundAdvisor: An event begins when the measured sound level exceeds at least one static or dynamic Trigger Level and persists longer than the Minimum Duration defined in the measurement setup. The even stops when the sound level drops 2 dB below the trigger level for longer than the Continuation Duration defined in the measurement setup.

With 831C-ELA firmware, event definition is defined by you – including threshold level, duration, and event continuation period when the SPL drops below the threshold level for a specific period of time. Triggering status icons identify event progression and qualification (see graph above).

The Model 831C can automatically generate an email alert to provide fast notice of any noise exceedance. The event alerts can be sent to a user configurable list of email addresses or by text message using an email to MMS gateway. Email event sound recording in conjunction with option 831C-SR.

The “Event” tab contains detailed information on each event including:

• Time and duration of Event
• Leq, MIN, MAX and PEAK SPL
• Frequency analysis of event (with 831C-OB3)
• Sound recording for source characterization (with 831C-SR)
• Event time history (with 831C-LOG). Event time history period can be different than that used in overall TH measurement.
  

A DYNAMIC trigger method can also be selected. The dynamic trigger is set to trigger when L85, L90 or L95 is exceeded by a predetermined number of decibels. A rise time can also be specified to determine how quickly the meter responds to changes in the background noise level. By utilizing the dynamic trigger, the number of false triggers is reduced and events (significant noise above background level) are better determined. Learn more about dynamic triggering.