Sound measures

You have measured the sound with hearing aids are equipped with two microphones that continuously sense ambient sound. This is primarily used for hearing-aid signal processing to enable optimal noise reduction, beamforming, and other processing features. However, we can also log the sensed sound to research the typical sound environments that hearing-aid users are exposed to, and how feelings, behavior, stress, and other factors differ between these environments. Note that the logged sound cannot be used to re-construct what has been said!

Sound pressure level (SPL) in Decibels

The sound you are exposed to changes constantly depending on your activity and location. Therefore, it is interesting to inspect a time series of the sound. This can help you better evaluate if some places had better sound quality than others, and if this corresponded with your own experiences and recollections.

The intensity of the sound is typically measured in sound pressure level (SPL). Below you see the time series of the SPL during your Wednesday and Thursday together with the labels of listening activity you selected.

Instead of inspecting single time series, we can also average them across all teams. This way, patterns will reveal common exposure that you all had - perhaps because you were doing group activities or the like. Below you can see the SPL average across data from each team.

Clearness of the sound (signal-to-noise ratio, SNR) in Decibels

Another dimension of the sound you are exposed to is its clearness, or the ratio between what you want to hear (e.g., speech) and disturbing background noise. This is typically measured as the signal-to-noise ratio (SNR), which estimates the difference in decibels (dB) between the target signal and noise. However, in real life, target signals are rarely well-defined—speech from one person can be both a target or noise depending on the listener’s intention. Thus, representing sound clearness using SNR is only a crude estimation of real-world perception.

As hearing aids optimize for speech reception, their estimation of SNR is typically based on the difference between ambient sound that is modulated in frequency and amplitude similar to speech, and unmodulated background noise. This means that the hearing aid will estimate high SNRs if there is a clear speech signal present, but it could also be music or a similar signal that contains modulation similar to speech.

Below, you can see time series of the sound clearness (SNR) you experienced on your trip.

Again, the average time series (shown below) better reflect how your days were different.

Noise dose

Loud sound can be harmful over time. The US-based Occupational Safety and Health Administration (OSHA) defines a “noise dose” that accumulates over time when exposed to sound pressure levels above a set threshold. Being in loud noise for a short duration is equivalent to being in less-loud noise for longer durations. The noise dose is defined as a percentage of the recommended maximum (100%) during a typical 8-hour working day. Source: https://www.castlegroup.co.uk/guidance/noise-at-work-assessments/dose/

Below, you can see how your noise dose evolves over time from 12:00 to 20:00 on Wednesday and from 9:00 to 20:00 on Thursday. Zoom in and navigate to explore your sound exposure!

Sound map

The sound you were exposed to is shown on the map below. You can choose to view “Sound pressure level” “Clearness,” or simply see where your group moved and when it happened. If you select “Time,” each dot is colored according to how much time (in hours) has passed since you started.