4. Conclusion

Following the emergence of the first industrial applications of active control in the 1990s, the 2000s saw the marketing of numerous products covering fields as varied as helmets, silencers, home protection and transportation. A good indicator of the growth of active control over the last few decades is the significant increase in the number of patents relating to this technique. A 2023 search of the Google patents database by Elliott et al. showed that 1,989 patents had been granted since 2011, compared with just 938 for the period from 1930 to 2010