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The Limitations of Speech Rec & How to Combat Them - Plum Voice - Blog

The Limitations of Speech Rec & How to Combat Them

Automatic Speech Recognition (ASR) is pretty cool technology. Simply say something and a machine will do what you ask it to do. Usually.

When an ASR grammar is tuned properly and the call conditions are good, ASR works really well.

Unpacking that last sentence should help you understand a bit more about ASR, how it works, and how to recognize when to implement it.

Because let’s be honest, ASR provides a great customer experience, but no technology is perfect. You should be aware of some of ASRs limitations before going too crazy with it.


We’ve talked about ASR and how it relates to natural language processing, and even artificial intelligence so we don’t need to spend too much time on grammars. Nevertheless, grammars are the part of the speech rec system that is programmed with all the different utterances that could constitute a valid response to a prompt.

If an IVR asks you a yes/no question, there are tons of different ways to say ‘no’: nope, nah, nuh uh, no, etc. When people talk about tuning a grammar they’re talking about listening to all the different ways callers respond to prompts to ensure that those specific utterances are in the grammar.

For companies with broad national or global reach, this issue is compounded when you factor in different accents and dialects.

Connection Matters

As important as grammars are, it’s equally important to pay attention to phone connections. Any call that goes into Plum’s (or any other) IVR platform will traverse the PSTN at some point. The PSTN’s bandwidth is limited so all audio that travels across it is down-sampled and compressed to 8bit, 8kHz.

Remember tape dubbing? If you made a copy of a VHS or a cassette the copy wasn’t quite as clear as the original. If you made a copy of the copy, the third-generation copy was degraded even more than the previous copy. That’s essentially what’s happening with the down-sampling and compression.

This matters for speech rec because you want the ASR engine to have the highest quality audio possible when it tries to decode utterances.

There are other factors that affect audio quality as well. Jitter from VoIP phones, static on the line or a bad connection, and background noise all have a negative effect on audio quality.

This is one of the reasons that Plum prides itself on using only Tier 1 telecom providers with our cloud IVR platform. We want you to have the best audio connection and call quality possible.

Safety Valves

There are many pieces that go to the phone connection puzzle. And it’s important to remember that not every caller will be doing so from a busy city street undergoing major construction.

Still, you want all your callers to have a great experience. So here are a few tips to help those callers who run into issues with ASR.

  1. Even if ASR is your first choice for your callers, make sure that you provide DTMF options.
  2. If the ASR is having trouble understanding a caller’s responses, don’t continually re-prompt them or disconnect the call. Set a reasonable re-prompt threshold and then switch to emphasizing DTMF input instead.
  3. Make your prompts non-bargable. A bargable prompt is one where callers can input their response before the prompt finishes. With ASR enabled, activating the barge-in feature at the same time can have a negative effect.

Fortunately, with a modern, feature-rich IVR development platform, like Plum Fuse, you don’t have to worry about wasting a ton of development time planning for these exceptions. Fuse makes it easy to manage ASR, giving you granular control over when and how it’s used in your IVR applications.

Schedule a demo of Plum Fuse today to learn more.


Publish Date: November 2, 2017 5:00 AM

2021 Buyers Guide Headsets

Premium Listing

Jabra is a leader in engineering communications and sound solutions – innovating to empower both consumers and businesses. We are committed to letting people hear more, do more, and be more than they ever thought possible. Through sound and video, we help transform lives. Jabra engineering excellence leads the way, building on 150 years of pioneering work. This allows us to create integrated headsets and communications tools that help professionals work more productively; wireless headphones and earbuds that let consumers better enjoy calls, music, and media; and pioneering video conferencing solutions, enabling seamless collaboration between distributed teams. Jabra employs approx. 1,400 people worldwide
PH: 800-826-4656

All Ears Ltd

Freemate headsets, and sanitary solutions for headsets
Freemate headsets available, corded and wireless for telephony and USB. 3 year warranty compatible with all model phones. We supply accessories from downleads, USB leads, ear cushions, leatherettes and we service call centre headsets, these are sanitised and repaired or serviced as required.

We supply the corporate environment, Government departments, security, medical and professional offices and meet the needs of many of New Zealand's SOHO market.

We can even develop and create one-off solutions for those with mobility or disability limitations opening up a world of freedom in communications. And we like to have fun on the journey.
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Comfort Telecommunications

Smith Corona Headsets
3 year warranty compatible with all model phones. Accessories also available. Cords, earpads, etc all factory direct pricing
PH: 800-399-3224




Since 1998 Headsets123 has been supplying Call Center Grade corded phone headsets, wireless headsets, headset telephones and a wide range of headset accessories to accommodate Medical, Insurance, Financial offices and large Call Centers environments offering you value, comfort, flexibility and increased productivity in your day to day business.

Our offices are located just outside of Seattle, WA. We hope you enjoy our wide range of headsets and accessories.

JPL Telecom

Based in Dorset, England, JPL designs and manufactures innovative professional telecom headsets. We have a wide range of professional telecom and call centre use headsets in wired, wireless DECT and Bluetooth styles.

Making sure that your customer’s voice can be heard is vital. JPL Telecom ensures that your customer’s experience is first-class. All headsets have our Surround Shield™ noise cancellation to make certain your customer only hears what you want them to hear. Comfortable and attractively designed headsets are built to withstand the constant use in any call centre environment.

Our aim is to continuously improve customer choice, offering a fair price and value to our resellers and end users.
PH: +44 (0)1258 820100

Unicom Services Ltd.

Contact center headsets and conference solutions
Unicom Services Ltd. is a distributor of professional headsets and communication solutions for all possible applications.

Products and Services:
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* Unified Communication Solution.
PH: +35924110203

Xiamen Mairdi Electronic Technology Co., Ltd

Call Center Headsets
Mairdi is a professional call center headsets maker in China. We've designed, produced and exported professional communication headsets for 16 years. Our headsets were exported to over 120 countires in the world.
Our headsets are widely compatible with nearly all IP Phones, desk phones, PC and mobiles. They are all noise cancelling and with built-in hearing protection technology. Our headset accessories are Plantronics or Jabra compatible. All the headsets and accessories are CE,FCC, RoHS certificated.
PH: 0086-592-7177232

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