1. Goal

Document audio volume limits for FRC events and provide a clear, consistent method for performing audio volume measurements.

2. Overview

FRC events are designed to be a fun and exciting experience for young participants and parents. However, negative feedback regarding audio volume has persisted among both attendees and volunteers for many years. FIRST provides cross-program guidance for acceptable audio volume levels at events (link). This document is designed to complement those guidelines, not supersede them.

The CDC website provides documentation that clearly outlines the long-term effects of hearing loss in humans. In some cases, it also provides some of the psychological outcomes of exposure to ranges of volume levels. The OSHA Technical Manual (OHM) also discusses short-term and long-term effects of exposure to elevated noise levels. In both cases, the commonly accepted volume levels deemed acceptable for limited exposure without hearing protection is defined as 70 ~ 85dB. OSHA guidelines further define frequency ranges that may be more damaging to human hearing. This document will focus on average noise levels.

3. Volume Limit

As mentioned above, several regulatory bodies define the audio volume limit for limited exposure as 85dBA average. However, FIRST-provided guidelines list 90dBA as the target limit. Moving forward, this document will reference 90dBA as the measurement target limit.

4. Measuring Audio Volume

Many specialized hardware and software solutions exist for measuring audio volume, however, it is important to ensure that measurements are performed consistently and fairly across different events and venues. Additionally, test procedures outlined in this document should be performed routinely (throughout the event) to ensure that compliance (and by extension, participant safety) is maintained.

4.1. Measurement Hardware and Stimulus

Specialized measurement hardware is not required to perform repeatable, accurate measurements of the average audio volume. However, care should be taken to ensure that measurements are both repeatable and reliable. The list below highlights requirements that should be met in order to perform fair, reliable measurements:

Only devices that offer microphone calibration functionality should be used. Low cost, handheld devices are readily available on Amazon, McMaster, etc. and are suitable for performing reasonably accurate measurements.

Apple mobile devices (iPhones) integrate per-device calibration in their production and manufacturing process. Because of this, iPhone-based audio volume measurements are acceptable so long as the phone is removed from any protective case and held upside-down (charging port towards the ceiling) during measurement.
Due to the diversity of Android-based devices, audio calibration data is not typically provided to app developers. Because of this, Android devices should not be used for audio volume measurements.

All audio EQ adjustments should be completed prior to measurement. As stated above, certain frequencies may be more damaging to human hearing than others. A best-effort EQ should be chosen prior to testing to avoid unintended shifts in perceived audio volume.
A “worst-case” approach should be taken to measurements. The goal of this effort is to avoid damage to human hearing, so a bias towards reducing audio volume should be maintained.
Test audio should reflect actual use cases. Measurements should only be performed while game music is playing and a person (preferably the GA or Emcee) is energetically talking. Performing measurements under conditions significantly different from actual use cases does not align with the intent of this document (minimizing hearing damage to participants and volunteers).

4.2. Measurement Locations

Care should be taken to minimize audio volume for all event participants. Because of this, audio volume measurements should be recorded at places where either teams, volunteers, and/or spectators are likely to reside. The figure below highlights several recommended areas where measurements should be taken (areas labeled “A” and “B”).

Additionally, measurements should also be recorded in the pits if a PA system is in use. Due to the space constraints usually imposed on pit spaces, measurements should be taken at the pit location nearest to the speaker / PA system (area labeled “C”).

4.3. Measurement Data Collection (Peak Measurements)

In an effort to simplify audio volume measurement and lower the barrier to entry, several peak measurements should be averaged to ensure that measurements are repeatable. Averaging instantaneous samples rather than peak samples may lead to artificially lower audio volume measurements and should be avoided.

Most handheld audio meters are likely to have a “peak hold” function that will only update the display as higher peaks are perceived by the device. App-based measurements should also use this functionality where available, and apps that do not have this functionality should be avoided.

Peak audio volume measurements are likely to occur while a person is speaking through a microphone, so care should be taken to test worst-case scenarios such as excited talking, yelling, etc. Music should also be played back simultaneously during testing. Once measurements have been collected, the system volume should be adjusted to a level believed to be sufficient and tested again. Once an acceptable volume has been found, it should be documented such that the acceptable limit can be quickly recalled.