Application of advanced DSP technology in hearing aids
Published time: 2020-02-20 18:05:29
Few applications face more technical limitations than modern hearing aids. Here, the need to increase performance levels and reduce power consumption in smaller designs is greater than consumer electronics.
By integrating more sophisticated digital signal processing (DSP) semiconductor solutions, manufacturers will be able to meet these needs of hearing aid users. The following sections detail the various design considerations affecting DSP technology and their use in today's hearing aids.
In simple terms, hearing aids work as follows. The sound waves are received by a microphone and converted into an analog electrical signal. An analog-to-digital converter takes this analog signal and converts it into a digital signal. It is then processed and adjusted with a DSP algorithm. This digital signal is then reconverted into analog form, passed to the receiver, and converted into sound waves heard by the hearing aid user. In order to minimize the visual impact of these devices and improve wearer comfort, more discrete new models were introduced. Commonly used BTE devices are now being replaced by hearing aids located deeper in the ear canal, such as deep ear canals (CIC) and invisible ear canals (IIC) devices, or miniature earmuff devices (also known as miniature behind the ear or OTE) ). The "hear but not see" trend of hearing aids requires the miniaturization of a large number of systems to integrated circuits that power devices.
Original equipment manufacturers (OEMs) are exploring IC solutions that implement hearing aids' unique data signal processing algorithms. This will support a more energy-efficient "platform" strategy in place, with different hearing aid models created from co-core DSPs. For example, mild hearing impairment can be addressed by a specific set of algorithms, while high-power devices, which address severe hearing impairment, can use the same platform, but are distinguished from additional gain or functionality and performance.
Wireless interoperability with portable electronic devices
There has been considerable interest in using wireless technology to enable audio signal transmission between hearing aids and electronic devices such as smartphones. Through the 2.4 GHz band (based on Bluetooth and ZigBee wireless standards), wireless interoperability allows hearing aid users to experience audio directly from electronic devices. For example, users can stream music from a handheld device or use their hearing aid as a headset to make calls. Wireless interworking can also enhance the interaction between users and devices. With a smartphone, hearing aid users can easily adjust and customize parameters and settings (such as volume control) without the need for cumbersome relay accessories. Since there are no clear standards for wireless technology, engineers must be able to quickly adapt to emerging standards such as Bluetooth Low Energy.
DSP architecture selection
There are many different types of DSP architectures available for modern semiconductors. Since this architecture will have a considerable impact on the overall energy efficiency of the hearing aid design, the OEM engineering team should ensure that they carefully consider the available options before making a decision to choose one.
A closed, fixed-function DSP is directly hardwired into the architecture to optimize system power and size. But this comes at the expense of system flexibility. Although some small parameters are still adjustable, the basic functions of the IC cannot be changed without major resetting work-this is expensive and time consuming.
2. Open Programmable Architecture
The open programmable architecture provides OEMs with improved design flexibility because DSP algorithms can be relatively easily modified. However, this flexibility is accommodated in a larger system, which does not meet the stringent power and size requirements of modern hearing aids.
3. Semi-programmable and application-specific, open programmable architecture
Alternative architectures that combine the beneficial attributes of closed and open programmability are now emerging. The basic DSP functions of the semi-programmable architecture are hard access logic modules and additional programmable DSP elements. Additional capabilities can be implemented in software. Although this provides some flexibility, semi-programmable architectures still have much larger power budgets than closed architectures. Application-specific, open and programmable architectures present another approach. Here, the DSP structure is designed and optimized in combination with an in-depth understanding of application requirements to handle specific signal processing requirements for specific applications. It has the software programmability of an open programmable architecture and the power efficiency of a power supply that is relatively close to that of a closed architecture. This architecture advances the platform solutions now needed by OEMs.
ON Semiconductor's Ezairo 7100 is a compact, extremely sophisticated system-on-chip (SoC) solution for the deployment of next-generation hearing aids. It combines an analog front end, an ARM Cortex-M3 processor, and a 24-bit quad-core DSP (application-specific, open programmable architecture) into a single semiconductor chip. The implementation of a closed and open programmable hybrid architecture means that the IC consumes less than 0.7 mA at a maximum clock speed of 10.24MHz operation. This can reduce system power consumption while still giving engineers the necessary design flexibility (adjustable algorithms) to create feature-rich hearing aid designs that stand out from the competition.
In short, the technology of the hearing aid industry is constantly changing-leveraging rapidly evolving innovations and targeting emerging markets. Strong competition and market demands for faster time to market have resulted in shorter product life cycles and the need for greater differentiation. Using ON Semiconductor's programmable or application-specific DSP technology, engineers will create smaller, feature-rich hearing aids that increase user comfort and satisfaction.Tag: DSP