Digital feedback suppression (DFS). Characterization of feedback-margin improvements in a DFS hearing instrument

Area of Science:

• Audiology and Hearing Aid Technology
• Digital Signal Processing in Acoustics

Background:

• Advancements in behind-the-ear hearing instruments include integrated digital feedback suppression (DFS) systems.
• Adaptive, digital signal processing necessitates novel evaluation methods for these sophisticated hearing devices.

Purpose of the Study:

• To describe a new measurement method for evaluating hearing instruments with integrated DFS.
• To assess the static feedback-margin improvement provided by the new DFS technology.

Main Methods:

• A specialized measurement technique was developed, focusing on the complex loop gain of the DFS instrument and its feedback path.
• The method was applied to real ears, requiring advanced test facilities like a dual-channel FFT analyzer and an anechoic room.
• Loop gain measurements were conducted on a new power behind-the-ear hearing instrument featuring DFS.

Main Results:

• Encouraging results were obtained from loop gain measurements on the new DFS power hearing instrument.
• Static feedback-margin improvements of approximately 10 dB were observed in groups of hearing-impaired children and adults.
• Measurement variations were most pronounced in users with custom ear molds and individually fitted instruments.

Conclusions:

• The described measurement method is effective for evaluating DFS hearing instruments, particularly on real ears.
• The new DFS power hearing instrument demonstrates significant static feedback-margin improvement.
• Individual fitting characteristics influence the variability of DFS performance measurements.