Mobile-Menu
German China

The Brain's Echo Filter How We Understand Speech in Noisy Environments

Source: Plos 2 min Reading Time

Researchers have discovered that the human brain processes direct speech and its echo as separate entities, enabling effective communication even in echo-prone environments.

Speech processing in an echoic environment.(Source: Jiaxin Gao)
Speech processing in an echoic environment.
(Source: Jiaxin Gao)

Echoes can make speech harder to understand, and tuning out echoes in an audio recording is a notoriously difficulty engineering problem. The human brain, however, appears to solve the problem successfully by separating the sound into direct speech and its echo, according to a study publishing February 15th in the open-access journal Plos Biology by Jiaxin Gao from Zhejiang University, China, and colleagues.

The audio signals in online meetings and auditoriums that are not properly designed often have an echo lagging at least 100 milliseconds from the original speech. These echoes heavily distort speech, interfering with slowly varying sound features most important for understanding conversations, yet people still reliably understand echoic speech. To better understand how the brain enables this, the authors used magnetoencephalography (MEG) to record neural activity while human participants listened to a story with and without an echo. They compared the neural signals to two computational models: one simulating the brain adapting to the echo, and another simulating the brain separating the echo from the original speech.

Participants understood the story with over 95 % accuracy, regardless of echo. The researchers observed that cortical activity tracks energy changes related to direct speech, despite the strong interference of the echo. Simulating neural adaptation only partially captured the brain response they observed — neural activity was better explained by a model that split original speech and its echo into separate processing streams. This remained true even when participants were told to direct their attention toward a silent film and ignore the story, suggesting that top-down attention isn’t required to mentally separate direct speech and its echo. The researchers state that auditory stream segregation may be important both for singling out a specific speaker in a crowded environment, and for clearly understanding an individual speaker in a reverberant space.

The authors add, “Echoes strongly distort the sound features of speech and create a challenge for automatic speech recognition. The human brain, however, can segregate speech from its echo and achieve reliable recognition of echoic speech.”

Citation: Gao J, Chen H, Fang M, Ding N (2024) Original speech and its echo are segregated and separately processed in the human brain. PLoS Biol 22(2): e3002498. https://doi.org/10.1371/journal.pbio.3002498

(ID:49917418)

Subscribe to the newsletter now

Don't Miss out on Our Best Content

By clicking on „Subscribe to Newsletter“ I agree to the processing and use of my data according to the consent form (please expand for details) and accept the Terms of Use. For more information, please see our Privacy Policy. The consent declaration relates, among other things, to the sending of editorial newsletters by email and to data matching for marketing purposes with selected advertising partners (e.g., LinkedIn, Google, Meta)

Unfold for details of your consent

Related content