The Problem with Speakerphones

The Problem with Speakerphones

We've all got speakerphones on our mobiles, but why are they so terrible to use?

In the cellular industry, lost conversation is serious business. Network operators know voice quality is responsible for a large percentage of their churn. This equates to billions of dollars of lost revenue every year as many customers blame poor sound quality as the primary reason for switching providers. The addition of speakerphones to the mix multiplies the potential for poor quality, but the industry does not have to accept it as a foregone conclusion - there are solutions available today that fix the problem.

Expectations of sound quality are rising as many consumers want to make their cellphone their only phone, but the voice quality is limited. In fact, there is also a push to move cellphones onto the business user's desktop, but not until voice quality improves.

Integrated Speakerphones
More and more mobile devices, including the latest cellphone models, smartphones, and PDAs, have integrated speakerphones, a necessity given increased demand (much of it generated by carrier campaigns) for freedom and mobility. To truly achieve this, users need simultaneous access to voice and data - a converged device that enables them to talk and take notes or access information at the same time.

The uses for such a device are numerous. Car travelers wish to simply throw the phone down on the passenger seat and answer using voice-activated command, allowing them to keep both hands on the steering wheel. Business users often receive cellphone calls on which they would like to allow multiple people to participate. Home users wish to allow the entire family to take part in a conversation instead of passing the phone around the room or having to relay an entire call to others after hanging up.

Integrated speakerphone functionality is imperative for these uses, and more manufacturers are integrating it into mobile devices to quench consumer demand for this feature. However, most speakerphones only magnify the sound-quality problem.

Issues and Limitations with Today's Technology
One limitation to existing speakerphone-enabled devices is the unnatural way they deal with echo. The way to solve echo and background noise for normal handset use is very different from the solution when in speakerphone mode. Many existing cellphones simply use the same handset echo-cancellation techniques in this more complex speakerphone environment. As a result, the communication becomes choppy and part of the meaning is lost.

A cellphone is designed so everything sounds good to the cellphone user, but often this is achieved at the expense of the other side of the call. A cellphone is basically a radio that receives and transmits information. Most phones favor the information they receive over the information they send, resulting in the recipient missing parts of the conversation. Many people cite poor performance as a reason for not using a cellphone exclusively. In fact, a recent Psytechnics poll of U.S.-based cellphone users found that 82% are frustrated by mobile networks' lower call quality.

Existing speakerphone technology may be "good enough" for early adopters who can see the value of mobility and convenience of the speakerphone, but in a mature market this will change. Minimal echo cancellation is sufficient for handset mode operation and is found in most off-the-shelf standard baseband chipsets. For speakerphone operation, better performance is needed to achieve good voice quality, speech intelligibility, and full-duplex communication.

Full-duplex communication refers to natural conversation flow - just like a face-to-face conversation. Full-duplex operation eliminates the misunderstanding that comes from syllable or word clipping. Without full-duplex capability, conversations can be fatiguing because people have to use extreme concentration just to make out the meaning as well as time their interrupts during pauses in conversation. No wonder most people still reach for a wired phone when they have an important or long phone call to make!

Of course speakerphone performance could be better and the bar for consumer expectation of sound quality is rising. But there is much more to speakerphone functionality than just adding a big speaker. Some ways speakerphone sound quality can be improved include:

  • Clear sound on both near end and far end of call
  • Higher speaker volume
  • Overlapping speech for both parties (as conversation shifts from one dominant speaker to the next - this is called "full-duplex")
  • More natural sound, like a face-to-face conversation
  • Reduced background noise to improve voice clarity

    A speakerphone-enabled cellphone that incorporates these characteristics and enables natural communication without lost intelligibility will allow users the freedom and mobility that has been promised by cellular campaigns.

    Available Solutions
    Cellphone users are unanimous that the voice quality of cellphone calls is unacceptable. Traditionally, handsets and networks are designed to favor the cellular user - the person on the other end of the call suffers. Unintelligible speech and choppy words are heard at the "far-end" of the call. The cellular user assumes that since he or she hears everything okay that the call is going well. Herein lies the paradox and issue of improving cellular sound quality.

    There are many challenges in a cellular phone environment that can cause poor sound quality. Sound-quality problems include lower speaker volume, speaker distortion, environmental acoustics, echo, background noises, delay from satellite or cellular networks, different voice power levels, and word clipping. Cellular users and network operators are demanding products that solve the problem of poor voice quality caused by echoes and harsh noise environments. One solution transforms the mobile appliance into the only phone needed by enabling natural conversation and simultaneous access to voice and data.

    As phones get smaller and smaller, there is a technical challenge, introduced by the reduction in distance between the speaker and microphone, with direct coupling, which makes acoustic echo more difficult to eliminate. Also, with integrated speakerphone functionality, volume from the speaker increases, which can lead to more acoustic echo feedback and system instability. With cellular phones integrating PDA functionality, the speakerphone capability is essential so that users can talk and access information on the PDA at the same time, and technologies applied in this area can also enhance the voice-recognition applications we're starting to see on these devices.

    In addition to good acoustical plastic design with mechanical isolation between the speaker and microphone through the use of non-sound-conduction materials and clever industrial design, it is imperative to have high-quality echo cancellation and noisereduction software to optimize sound quality. While echo cancellation has historically been done in hardware, the modern processors often found in mobile equipment are now more than capable of providing a complete software solution, making it cheaper to deploy and more flexible to use.

    Such software integrates key technologies to improve voice clarity: acoustic echo cancellation, bidirectional noise reduction, and sound enhancement. The technologies have to be optimized for performance, MIPS, and memory for fear of affecting the radio communication that is central to the phone function. Whereas older designs of handsets had only one processor, meaning that echo cancellation would have to share processing with the radio stack, most mid-range handsets now have a separate processor, which removes the risk of an application having any impact on the radio functions. By being able to access data on a phone/PDA combination while speaking, careful use of sound enhancement transforms the mobile appliance into the only phone you need by enabling natural conversation with simultaneous access to voice and data.

    Several enhancements for improved speech intelligibility can be integrated in software with graphic equalizers and speech emphasis. Much like stereo equipment, these features help with tuning and provide improved presence and fullness of voice. Another sound enhancement feature is prespeaker compression to reduce non-linear effects and prevent speaker distortions.

    If mobile phones are going to replace their wired equivalent, then quality speakerphones are going to be essential, but even the video calls we're already seeing on 3G networks in Europe require speakerphone capability. Only by accepting that current standards are unacceptable can manufacturers start to understand how to improve them, and then we'll all be able to hear what's going on.

  • More Stories By Jim Jacot

    Jim Jacot is a vice president at Acoustic Technologies, where he works closely with cellular network operators, handset vendors, and chipset manufacturers. He holds an MBA from Arizona State University and a BS in computer engineering from Iowa State University.

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