100 Things #24: ePRB (Perceptual Rub & Buzz Measurements)

Not all distortion is audible. Perceptual Rub & Buzz measurements identify only those devices with audible Rub & Buzz defects, rather than all Rub & Buzz defects. Basing end-of-line pass/fail decisions on this metric increases yield while maintaining customer satisfaction.

ePRB (Perceptual Rub & Buzz Measurements)

Learn more about enhanced Perceptual Rub & Buzz

Our full ePRB launch seminar goes in-depth with algorithm explanation, testing demonstrations, use cases, and more.

For all things Enhanced Perceptual Rub & Buzz including listening examples, published articles, and a sequence to try ePRB for yourself, check out our Enhanced Perceptual Rub & Buzz page.

Video Script:

While conventional Rub & Buzz measurements identify faulty products and provide valuable information about the health of your production line, they can sometimes result in devices with inaudible distortion artifacts being rejected. To maximize yields, perceptual distortion metrics enable the rejection of only devices that actually sound bad.

SoundCheck is the only audio test system with a  perceptual Rub & Buzz metric that offers excellent correlation with subjective perception and sufficient noise immunity for production line use. 

We led the way with research in this area here at Listen. In 2011, we launched the first Rub & Buzz algorithm built on a model of human hearing . This original model was well received due to its excellent correlation with subjective listening tests. However, like the human ear, performance was less repeatable in the presence of background noise. Many hours of original research over the past few years have resulted in our new Enhanced Perceptual Rub & Buzz algorithm. This  combines our original methods with proprietary noise suppression and a refined perceptual model to exceed the performance of the human ear. In other words, it replicates the hearing characteristics of a human ear in a quiet environment, even in the presence of background noise.

This means that it offers the excellent noise immunity needed for a wide range of manufacturing environments.

Let me show you what I mean.

These graphs show 3 speakers, a good, bad and borderline loudspeaker, each measured 10 times using 3 different perceptual Rub & Buzz algorithms; our original 2011 version, our new ePRB algorithm, and a perceptual algorithm from another audio measurement company. You can see that while all three indicate the relative magnitude of the distortion, in both our original algorithm and the ‘other’ algorithm, the variation in the repeated measurements for each speaker is inconsistent enough that it would be problematic on the production line. Our new algorithm, the middle graph, clearly shows much greater repeatability between measurements. This offers a high level of confidence in the results and makes it easier to set limits.

Correlation to subjective tests is also improved through the use of more comprehensive masking curves that include additional factors to more  accurately replicate the human ear’s behavior and reveal increased detail in the ear’s highly sensitive 500Hz – 2kHz range. 

Perceptual distortion metrics are a valuable end-of-line test addition as they  increase yield by passing products with inaudible distortion. That said, in most cases, it is desirable to also measure normalized Rub & Buzz and Loose particles, as these are convenient ways of monitoring your production line for early warning of any problems that could eventually lead to a returned product from a customer.

All three distortion measurements, along with a whole host of other end-of-line parameters can be made in SoundCheck simultaneously, using the same stepped sine sweep stimulus signal. In other words, there is no increase in test time when you add perceptual metrics to your end-of-line test. Check out our website for more detailed information, demo sequences to try this out, and more.