The constraints inherent in thinner, lower-cost audio system designs typically degrade audio quality, but scalable audio tuning methods can overcome these limitations.
In today’s world, the market wants technology to be smaller, thinner, sleeker while still delivering great sound. As our devices have gotten smaller, so has the amount of space for audio gear. Additionally, the cost pressure on the product puts additional pressure on the audio hardware to reduce the cost as well. This often requires a cheaper, finer sound system solution. These constraints will degrade the audio quality. However, this is where solutions offering optimized signal chains come into play, relying on scalable audio tuning methods that can improve the audio performance of any device.
What is an audio signal chain and how does it work?
An audio signal chain is the path taken by the audio input signal through electronics and processing software to output. An example of this is a television. The program source is received by television equipment and the video and audio signals are separated into two paths. The audio is first processed by a decoder. This is usually a large digital signal processor (DSP) to decode audio from the format it was recorded in, into an audio stream that can be used by the specific product. If sound will only be rendered (output) from the two TV speakers, then the DSP will need to process (downsample) all multichannel signals to stereo only. If the audio is to be rendered to a soundbar connected to the TV, the signal will need to be downsampled to the correct number of channels for that soundbar (soundbars can be two to ten devices).
Audio signal chains can range from simple to very complex depending on the number of changes or effects needed. Having a powerful audio processing tool allows audio and system engineers to develop a signal path to optimize audio quality within hardware constraints. The goal of the audio signal chain is to provide sound that is the best representation of the original recording.
What are the challenges of optimizing signal chains?
Each audio system is unique to a specific product and each architecture has its own issues. Some of the issues that audio system architects deal with include output level, voice clarity, bass level and extension, and high frequency directivity.
- Overall output level, or the overall “volume” of the product, should provide a comfortable listening level above ambient noise. The volume will be limited by the size of the audio speaker’s speaker power rating, system gain structure, interfaces such as wire gauges, and audio power amplifier. Maximizing the output level will require a dynamic multiband approach as hardware will have different limitations in different frequency ranges.
- Clarity of voice is another problem with many products. Human hearing is sensitive to the frequency range of the human voice. Specific frequencies can be “scrambled” with other types of sounds in an audio stream. The ability of audio processing to “extract” voices can make a big difference in product satisfaction.
- Bass level and depth are two features that most listeners always want more of. To produce a balanced bass level and reproduce the lowest bass possible, several techniques are used. One technique is “Smart Bass”. This technique sets a bass level goal and attempts to achieve that level until hardware limitations restrict it. Most systems can produce bass above this level, but severe distortion will also be produced. Balancing bass output and lowest distortion is best achieved with a software processing tool such as Harman AudioEFX.
- High frequency directivitybecomes a problem when the speakers are not aimed directly at the listeners. The higher frequencies are very directional and the listener who is “off-axis” will not hear this energy at the level expected. To address this, the audio architect will use a processing block that boosts the higher frequencies so that off-axis listeners hear a more balanced level. Power and processing operations are important on portable devices due to limitations in battery power and processor size. All of the processing mentioned above should be done in the most efficient way to maximize playback time.
What is the solution?
With the rise of small portable products producing booming bass and slimmer television systems, the need for advanced digital signal processing has increased. Tools like Harman Audio EFX that enable signal chain optimization use many audio algorithms, including smart bass, smart treble, voice enhancement, parametric EQs, compressors, and limiters. Using this type of tool, audio system architects can quickly design and test audio signal paths to produce the correct product audio “signature” in their DSP-based audio systems.
|Bruce Ryan started at Harman in 1999 and is an original member of the Home and Multi Media business unit, which developed the first Harman desktop, home and portable Bluetooth speakers. currently leads the Harman Integrated Audio An engineering group, Bruce and his team develop audio solutions for internal Harman products and external partners. He holds a BS and MS in Mechanical Engineering from CSUN and an MBA from Pepperdine University.|
|Nikhil Rathodproduct manager at Harman Integrated Audio, is a hardware and software innovator committed to helping people realize the full potential of technology. He has over 12 years of experience designing, developing and managing consumer technology solutions with a passion for defining viable solutions and exceptional user experiences. He holds a master’s degree in electrical engineering from CSUN.|
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