NEW YORK, NY — Scientists from Columbia University, led by Dr. Nima Mesgarani, have made significant strides in understanding how the human brain processes speech in noisy environments. Their research, published in the open-access journal PLoS Biology, combines neural recordings and computer modeling to reveal the brain’s remarkable mechanisms when it comes to deciphering speech amidst background noise.
One of the challenges faced by individuals trying to comprehend speech in crowded settings is the overshadowing effect of other voices. Increasing the volume of all sounds indiscriminately proves ineffective, while current hearing aids, designed to amplify intended speech, lack the necessary precision for practical use.
Exploring How Brain Handles Speech in Noisy Environments
To study how the brain handles speech in noisy environments, the researchers implanted electrodes in the brains of epilepsy patients undergoing surgery. These electrodes allowed the team to record neural activity while the patients focused on a single voice, even when it was obscured by another voice or subdued by it. Analyzing the gathered neural data, the researchers developed computational models that offered insights into how the brain encodes speech information.
The results of the study revealed intriguing findings. The brain encodes phonetic details of speech differently based on the ease of hearing and the listener’s attention. Both the primary and secondary auditory cortex play vital roles in encoding “glimpsed” speech, where the desired speech is partially obscured by louder voices. Importantly, the encoding of attended speech is more pronounced in the secondary cortex.
In contrast, the encoding of “masked” speech, where the desired speech is quieter than the surrounding noise, only occurs when it is the attended voice. Notably, the encoding of “masked” speech takes place later in the processing stages compared to “glimpsed” speech. These findings provide crucial insights into the brain’s mechanisms for speech perception in noisy environments.
Implications for Future Hearing Aid Technology
The implications of this research are far-reaching, particularly in the development of hearing aid technology. By decoding the “masked” segment of intended speech separately, auditory attention-decoding systems could be enhanced, leading to improved brain-controlled hearing aids that effectively isolate attended speech.
Dr. Vinay Raghavan, the lead author of the study, emphasized the brain’s ability to recover missed speech information when background noise is too loud. Additionally, the brain can capture fragments of speech that the listener is not directly focused on, but only when the intended speaker’s voice is relatively quiet in comparison.
This latest research offers new avenues for potentially refining today’s hearing aid technology and improving speech comprehension in challenging acoustic environments.
- Raghavan VS, O’Sullivan J, Bickel S, Mehta AD, Mesgarani N. Distinct neural encoding of glimpsed and masked speech in multitalker situations, PLoS Biology (2023). DOI: 10.1371/journal.pbio.3002128