Dual SPL Traffic Light

Dual SPL Traffic Light

Dual SPL Traffic Light allows you to monitor sound levels using two different methods. For example, watch the A-weighted SPL and the peak levels at the same time, or run an LEQ (long term average level) while keeping an eye on C-weighting.

You can also set the trigger levels for the colors, and even trigger Apple HomeKit lights to change color with the sound levels.

Operating instructions are below the video.

Dual SPL Traffic Light Instructions

Dual Traffic Lights

The settings for each traffic light are independant. You can setup one as Fast, the other as an Leq. Each can have different color trigger dB levels. To switch the settings page to one of the SPL Traffic Light, just tap the selector on the top of the page.

Color Trigger Levels

Enter the dB level at which to trigger the traffic light color. Levels lower than the green setting will show as gray on the screen.


Enter an offset if you need to adjust the level to meet local requirements. Normally, leave this field set to 0.0 or blank.

Select Fast or Slow exponential decay, or one of the provided Leq times. If an Leq time is selected, the Leq Type selector will appear. Choose Leq Restarts to run consecutive Leq tests, or choose Running Leq to calculate the Leq from the last n seconds or minutes.


Select the desired weighting, Flat (Z), A, C, or one of the octave bands, 32, 63, 32+63, or 125Hz.

Notification Instructions

Notifications can be used to send emails when the Fast, Slow, or average sound level (LEQ) exceeds a pre-set threshold.

Email Setup

Email does not need to be setup on the iOS device, since we use our own email server. An internet connection is required, either over wifi, or via cellular data connection. Both of the email addresses, if set, will receive the same notification. You can also enter an email subject line that will appear on the notification email.

Trigger Condtions

Notifications will be triggered and emails sent when the display for the selected traffic light turns red for at least one second.

Start / Stop emails

If turned on, you will get a notification each time that the play / pause control changes state. Thus, you can know for sure if a test was running by looking for the start and stop emails in your inbox.

You can select a particular traffic light for notifications, either traffic light, or only send notifications when both traffic lights turn red.


If a notification is sent, the next notification will not be sent until at least this much time has passed. Use this to prevent getting emails more often than you wish.

Email Limit

Set this value to limit the number of emails that will be sent per SPL Traffic Light test. Restarting a new SPL Traffic Light test resets this counter.