Audio processing in wireless earbuds (Several assignments with the company Dopple)

Dopple is a Dutch company designing, developing, and manufacturing wireless stereo headsets for the professional and consumer markets. Adding to its portfolio, Dopple is inventing and developing new technologies for wearable communication devices providing hearing protection in noisy environments. To help Dopple develop these new technologies, various projects are available in the area of audio signal processing. Students may work on location (Assen) or remote at the TU Delft.

Assignment

Audio processing in wireless earbuds (with company Dopple)

1.  Dopple GroupChat

Dopple has developed a new communication, protocol Dopple GroupChat (DGC), which operates on top of the Bluetooth radio. DGC allows users to communicate directly towards one another without the intervention of a smartphone, tablet, or laptop. Groups of users in radio range can thus communicate in a full duplex fashion. Applications can be found in sports (think of cycling, jogging, and fitness centers), hearing impaired people, and people working in noisy environments. Communicating within a group places special requirements on the audio processing. Audio signals may reach the participants via different paths, both acoustically and electronically. Audio delays may differ depending on the path considered, creating echoes. In addition to the voice signals, the microphone may also pick up correlated or uncorrelated disturbing signals like wind or environmental noise that may hamper the voice communications. Adaptive audio processing is needed to accommodate for changing environments.

2.  Bone Conduction

In addition to air microphones for picking up the voice via sound waves in the air, the Dopple wearables contain sensors that pick up the sound waves that propagate via the skull, so called bone conduction sensors. Bone conduction offers a great way to suppress disturbing audio signals like wind and environmental noise. However, because the sound waves have to propagate through human tissue (skin, bones), the voice quality is affected, suppressing high frequency components. Methods are sought to process the voice signals to let them sound more natural again.

3. Occlusion effect

To provide optimal hearing protection, Dopple designs custom-fit ear pieces that completely seal the ear canal. To the user, acoustically sealing the ear canal gives an uncomfortable experience due to the occlusion effect. The user hears her/his voice distorted (boosting the low frequencies) and also hears body sounds (swallowing, chewing, walking, and so on). As a result, wearing sealed ear pieces for a longer time is considered a nuisance. Dopple is looking for methods to reduce the impact of the occlusion effect. The Dopple wearables have in-ear microphones to apply Feedback Active Noise Cancellation (FB-ANC) by applying anti-sound to suppression environmental noise. Possibly, this can also be used to reduce the occlusion effect.

4.  Suppression of loud noise 

In noisy environments, voice pickup by air microphones is a challenge. Under low signal-to-noise ratio (SNR) conditions the noise dominates, making it difficult for the user to communicate via a wireless audio headset. Bone conduction sensors picking up the voice audio waves propagating through the bones of the user’s skull, are an attractive alternative. However, in case of very loud sounds like encountered in construction work or on a factory floor, the air waves also interact with the bone conduction sensor when they hit the headset housing. In these conditions, the SNR is too low for speech intelligibility, even with a bone conduction sensor. By using both the air microphone and the bone conduction sensor, a system can be designed that can filter out the noise in the bone conduction signal. Using adaptive filtering, the system adapts to the environment to cancel out the loud noise.

Requirements

About Dopple

Dopple is a Dutch private company designing, developing, and manufacturing wireless stereo headsets for the professional and consumer markets. It consists of a team of some 25 people, both seasoned experts having worked with wireless technology and products for more than 30 years, and young people at the start of their career. It is an inter-disciplinary team covering research, electronic engineering, mechanical engineering, and software engineering.

Dopple collaborates with various academic and applied universities and has a large base of partners both in the silicon and manufacturing industry. Dopple is located in Assen next to the central railway station.

For more information, please contact:

Jaap Haartsen, CTO & Chief Scientist at jaap.haartsen@dopple.nl

Contact

Last modified: 2025-01-28