Keyword Spotting Using Crosscorrelation

1. Keyword Spotting Using Crosscorrelation Presenters: BathiyaSenevirathna Roshan Rajeev Advisor: Dr. UchechukwuAbanulo Montgomery College Speech Processing Laboratory

2. Presentation Outline • Research Goal • Applications of Research • Method • Results • Demo Presenters: BathiyaSenevirathna Roshan Rajeev Advisor: Dr. UchechukwuAbanulo Montgomery College Speech Processing Laboratory

3. Research Goal Research Goal Applications of Research Method Experiment Demo • Keyword detection • Did the speaker say ____? • Keyword location • Where did the speaker say ____?

4. Research Goal Applications of Research Method Experiment Demo • Applications of Research

5. Research Goal Research Goal Applications of Research Method Experiment Demo • Interactive Voice Response • Telephone ticket booking • National Security • Conversation monitoring to identify words of interest

6. Research Goal Applications of Research Method Experiment Demo • Method

7. Crosscorrelation Research Goal Applications of Research Method Experiment Demo • Measure of similarity between two signals • Two signals compared by • Sliding one signal by a certain time lag • Multiplying both the overlapping regions • Repeating the process and adding the products until there is no more overlap • If both signals are exactly the same, there’s a maximum peak at the time = 0, and the rest of the correlation signals tapers off to zero Area Overlap

8. Crosscorrelation Research Goal Applications of Research Method Experiment Demo

9. Typical Cross-Correlation Results Research Goal Applications of Research Method Experiment Demo Keyword Match No Match See any differences??

10. A Closer look… Keyword Match Research Goal Applications of Research Method Experiment Demo • Much higher amplitude near zero-lag point • Rest of graph is almost zero No Match • No clear maximum points • Amplitude is generally the same throughout

11. The Algorithm Research Goal Applications of Research Method Experiment Demo Find average of points in the first 10% of the samples Find average of points in the last 90% of the samples Compute the ratio of the two values. If n = the number of samples in the crosscorrelation graph: Ratio =

12. The Algorithm Research Goal Applications of Research Method Experiment Demo 1. Let the length of the keyword or phrase be n. The cross correlation of the keyword and the first n samples of the utterance is computed. 3. Shift observed portion by a small amount and repeat process 2. If a portion is reached where the calculated ratio is above a defined minimum threshold then mark the location of the indices xcorr

13. Research Goal Applications of Research Method Experiment Demo • The Experiment

14. Experiment Research Goal Applications of Research Method Experiment Demo • Effectiveness of the algorithm in finding keywords in a speech utterance • 8 speakers, mixed gender • Threshold varied from 6 to 15 • Criteria: • Hit: >50% of keyword length found in correct location • False Alarm: 2 x length of keyword found in wrong location

15. Criteria - Hits Research Goal Applications of Research Method Experiment Demo Actual Location Wrong Location Miss! <50% of Word Found Miss! >50% of Word Found Hit!

16. Criteria – False Alarms Research Goal Applications of Research Method Experiment Demo Actual Location (No Keyword) >2x Keyword Length Found False Alarm! <2x Keyword Length Found No False Alarm! No Keyword Found No False Alarm!

17. Results Research Goal Applications of Research Method Experiment Demo Performance of Algorithm at Different Threshold Levels At a threshold of 8: 4/8 keywords were found 1/8 utterances with false alarms

18. Summary Research Goal Applications of Research Method Experiment Demo • Crosscorrelation is a versatile tool for keyword spotting • This was just one example of a possible algorithm • Further research to optimize performance

19. Research Goal Applications of Research Method Experiment Demo • Demo