Gregory M Ellis –
Pamela Souza –

Northwestern University
Frances Searle Building
2240 Campus Drive
Evanston, IL 60201

Popular version of paper 5aPPb2
Presented Friday morning, December 11th, 2020
179th ASA Meeting, Acoustics Virtually Everywhere

True scientific discoveries require a series of tightly controlled experiments conducted in lab settings. These kinds of studies tell us how to implement and improve technologies we use every day—technologies like fingerprint scanners, face recognition, and voice recognition. One of the downsides of these tightly controlled environments, however, is that the real world is anything but tightly controlled. Dust may be on your fingerprint, the light may make it difficult for the face recognition software to work, or the background may be noisy making your voice impossible to pick up. Can we account for these scenarios in the lab when we’re performing experiments? Can we bring the real world—or parts of it—into a lab setting?

In our line of research, we believe we can. While the technologies listed above are interesting in their own right, our research focuses on hearing aid processing. Our lab generally asks: what factors, and to what extent do those factors, affect speech understanding for a person with a hearing aid? The project I’m presenting at this conference is specifically looking at environmental and hearing aid processing factors. Environmental factors include the loudness of background noises and echoes. Processing factors involve the software within the hearing aid that attempts to reduce or eliminate background noise and amplification strategies that make relatively quiet parts of speech louder so they’re easier to hear. We are using computer simulations to look at both the environmental and the processing factors. We can examine the effects of the environmental and processing factors on a listener by seeing how speech intelligibility is affected by those factors.

The room simulation is first. We built a very simple virtual environment pictured below:

virtual restaurant

The virtual room used in our experiments. The red dot represents the listener. The green dot represents the speaker. The blue dots represent other people in the restaurant having their own conversations and making noise.”

We can simulate the properties of the sounds in that room using a model that has been shown to be a good approximation of real recordings of sounds in rooms. After passing the speech for the speaker and all of the competing talkers through this room model, you will have a realistic simulation of the sounds in a room.

If you’re wearing headphones while you read this article, you can listen to an example here:

A woman speaking the sentence “Ten pins were set in order.” You should be able to hear other people talking to your right, all of whom are quieter than the woman in front. All of the sound has a slight echo to it. Note that this will not work if you aren’t wearing headphones!”

We then take this simulation and pass it through a hearing aid simulator. This imposes the processing you might expect in a widely-available hearing aid. Here’s an example of what that would sound like:

Same sentence as the restaurant simulation, but this is processed through a simulated hearing aid. You should notice a slightly different pitch to the sentence and the environment. This is because the simulated hearing loss is more extreme at higher pitches.”

Based on the results of hundreds of sentences, we would have a better understanding of how the environmental factors and the hearing aid processing interact. We found that for listeners with hearing impairment, there is an interaction between noise level and processing strategy, though more data will need to be collected before we can draw any solid conclusions. While these results are a promising first step, there are many more factors to look at—different amounts of echo, different amounts of noise, different types of processing strategies… and none of these factors include anything about the person listening to the sentences either. Does age, attention span, or degree of hearing loss affect their ability to perform the task? Ongoing and future research will be able to answer these questions.

This work is important because it shows that we can account for some environmental factors in tightly-controlled research. The method works well and produces results that we would expect to see. If you want results from the lab to be relatable to the real world, try to bring the real world into the lab!

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