TU Ilmenau develops bio-inspired microphone for speech recognition

The Technische Universität Ilmenau, together with research partners, has developed a microphone inspired by biology that picks up sound similar to the human ear. The microphone could help improve speech recognition for controlling a variety of digital applications. In the future, the new process could even make overall acoustic systems consisting of a microphone and speech recognition more efficient, so that they consume less energy. The results of the research conducted by the Group of Micro- and Nanoelectronic Systems at TU Ilmenau and its research partners have just been published in the renowned international journal Nature Electronics.

Voice recognition technologies such as Alexa or Siri have made rapid progress in recent years. They can now understand voice commands very well, for example, to control cell phones, operate an alarm clock or even a wide variety of smart home applications. However, noisy environments with many different sounds, such as train stations, restaurants or streets, are still very problematic for current technologies with conventional microphones. The human ear, on the other hand, is able to pick out the voices of individuals in noisy environments with a lot of background noise and understand what is being said.

A team of researchers from the TU Ilmenau, the Christian Albrechts University of Kiel, the Karlsruhe Institute of Technology, the University College Cork and the Ilmenau Fraunhofer Institute for Digital Media Technology has now made use of the advantages of the human ear. In the process, the scientists are replicating the function of the inner ear, which supports hearing comprehension in humans, especially in noisy environments. The bio-inspired microphone they developed uses three properties of the human auditory system:
 

1. Sounds, such as a spoken word or a melody, consist of different tones. They can be recognized by speech recognition systems by decomposing the sounds into the tones they contain. In humans, this decomposition takes place not only in the brain, but already in the inner ear. This consists of a large number of small hair cells, each of which reacts to different sounds. This prevents the different sounds from influencing each other during hearing and prevents soft sounds from being masked by loud sounds. Unlike conventional microphones, the bio-inspired microphone breaks down sounds before converting them into an electrical signal.
2. In order to understand soft sounds, they must be amplified significantly. Loud sounds, on the other hand, in order to be perceived undistorted, must be attenuated. This ability of the auditory system allows humans to hear sounds whose sound pressure varies by a factor of one million. In the inner ear, this what experts call nonlinear or compressive amplification is already integrated into the sensor. This makes it possible to hear significantly wider ranges of loudness.
3. In quiet environments, it is relatively easy for people to pick out sound signals that are important to them, such as the voice of a single person. In noisy environments, however, this is difficult and the sound signals that are important to the listener must be amplified more than the ambient sounds for good listening comprehension. Therefore, in order to hear as well as possible in different environments, the sensors of the inner ear, the hair cells, are permanently adapted to the changing requirements. This is achieved by changing the relative amplification factors for individual sounds depending on the situation.