Tag Archive for: buzz

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.

100 Things #21: Normalized Rub & Buzz Measurements

In this short video, Steve Temme explains how SoundCheck’s unique normalized Rub & Buzz measurement method offers greater accuracy, high speed, and excellent noise immunity for production line testing. Additionally, analysis of each harmonic separately yields valuable information to help identify the exact production line fault.

Normalized Rub & Buzz Measurements

Learn more about normalized rub & buzz measurements

This technical note on Harmonic Distortion Measurement, authored by Listen president Steve Temme, explains the relationships between sampling rate, stimulus frequency and measured harmonics for both normalized and conventional harmonic distortion measurements.

Video Script:

Higher order harmonic distortion is an important production line measurement for identifying Rub & Buzz defects introduced in the manufacturing process. SoundCheck uses unique algorithms for measuring Rub & Buzz distortion and  ‘Normalized Rub & Buzz.’  Let’s look at how these differ from conventional methods.

There are 2 commonly used methods for measuring Rub & Buzz. The ‘tracking high pass filter’ method uses a high pass filter to remove the lower harmonics and sums the remainder. This combines all the harmonics plus transient distortion caused by loose particles into a single metric. While this gives an overall indication of distortion level, it reveals nothing about the cause of the distortion. It is also susceptible to background noise, which can result in false rejects on the production line.

A more accurate, but slower method, sequentially measures individual harmonics using a tracking filter that moves from one harmonic to  the next. While this provides accurate and detailed information on each harmonic, it is not fast enough to use on automated production lines.

SoundCheck’s unique Rub & Buzz distortion methods, which date back to the mid 1990s,  offer more accurate measurements, high speed and excellent noise immunity for production line testing. Furthermore, they analyze each harmonic separately which provides a wealth of additional information to help identify the exact production line fault

Let’s take a look at the unique features that make up the SoundCheck algorithms. 

Firstly, our proprietary Harmonictrak algorithm applies advanced filtering techniques to exclude the noise between the harmonics. All the harmonics are measured discretely and simultaneously. This is extremely fast compared to other methods, and also highly immune to background noise. Furthermore, because it measures each harmonic separately, it provides valuable information about the precise reason that the device failed the test. For example, high levels of harmonic distortion in the 10-15th order range usually indicate a rubbing voice coil, whereas distortion at the 50th harmonic and above is frequently caused by vibrating voice coil lead wires hitting the cone. 

SoundCheck also offers an enhanced version of this called Normalized Rub & Buzz. In this version, we compare the harmonic levels to the fundamental level at their measured frequency before their ratio is plotted, rather than the fundamental level at the excitation frequency. This is more accurate, because it removes the effect of the non-flat frequency response from the distortion. This makes it easier to see the peaks in the distortion response independent of the peaks and dips in the fundamental response, and easier to set limits.

Both these measurement options can use a stepped sine wave test stimulus, so they can be measured simultaneously with other end-of-line parameters such as frequency response, THD and even perceptual Rub & Buzz. While the main objective of Rub & Buzz detection is to identify faulty-sounding speakers, the individual harmonic analysis offered by SoundCheck’s algorithms makes them also valuable for continually monitoring production line performance for any drift in characteristics that could lead to product failure with customers.

Although these methods are now 25 years old, they still out-perform all other methods for measuring higher order harmonic distortion on the production line. More details on these unique algorithms can be found in the published papers section of Listen’s website.

Introducing Enhanced Perceptual Rub & Buzz (ePRB)

The new Enhanced Perceptual Rub & Buzz (ePRB) algorithm increases production line yield by rejecting only those speakers with audible Rub & Buzz defects. It offers excellent correlation with human perception, unmatched repeatability and reliability and is fast, adding no addition time to end of line tests. Watch the launch video to learn more about this ground-breaking perceptual distortion algorithm.

Introducing Enhanced Perceptual Rub & Buzz

Read on to learn 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.

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.

Listen’s new enhanced Perceptual Rub & Buzz algorithm is the first to perform better than the human ear. Its proprietary noise reduction technology and advanced perceptual algorithms make its performance in a noisy factory environment comparable to the performance of a human ear under normal listening conditions. In other words, it is the only perceptual Rub & Buzz metric that accurately correlates real-world end-of-line results with listener perception.

Furthermore, it is highly repeatable, simple to configure and set limits, and can be simultaneously implemented with other end-of-line tests with no increase in overall test time.