Active control of periodic fan noise in laptops: spectral width requirements in a delayed buffer implementation

 

H. A. Cordourier–Maruri*¹, F. Orduña–Bustamante²

 

^1,2 Laboratorio de Acústica y Vibraciones, CCADET Universidad Nacional Autónoma de México. *cordourier@hotmail.com

 

ABSTRACT

An active control system intended for the reduction of strictly periodic noise components in computer cooling fans is described, which is based on high–performance digital sound device architectures found in some personal computers. The system overcomes causality and synchronization constrains imposed by delayed buffering, as usually found in computer audio processing. Performance of the system is demonstrated and evaluated through measurements in a physical implementation of active noise control of synthetic tones combined with laptop fan noise, carried out under anechoic and slightly reverberant conditions. Tests on other types of tonal noise sources, like an electrical transformer, were also carried out. However, its wider applicability to the cancellation of tonal noise has been proved compromised by weak periodicity issues found and reported in this work. Also, a study of noise spectral width requirements for successful operation is presented.

Keywords: Computer noise, fan noise, tonal noise, periodic noise, computer cooling fan, active noise control.

 

RESUMEN

Se describe un sistema de control activo para la reducción de las componentes de ruido periódico en ventiladores pequeños de computadora. El sistema se basa en arquitecturas de sonido digital de alto desempeño, presentes en algunas computadoras personales. El sistema es capaz de superar las limitaciones de causalidad y sincronización provocadas por retardos en la operación basada en bloques de datos (audio buffers), que es usual en el procesamiento digital de audio en computadora. El desempeño del sistema se demuestra a través de mediciones en una implementación física de control activo de ruido de tonos sintéticos combinados con el ruido de ventilador de una computadora portátil. Estas mediciones fueron llevadas a cabo bajo condiciones acústicas anecoicas y ligeramente reverberantes. También se llevaron a cabo pruebas con otras fuentes típicas de ruido tonal, como un transformador eléctrico. Sin embargo, se ha probado que la capacidad de aplicación para cancelar ruido tonal está limitada por pequeñas variaciones en la periodicidad del ruido, determinadas y reportadas en este trabajo. Se presenta también un estudio experimental de los requerimientos en la anchura espectral del ruido para una operación exitosa.

Palabras clave: Ruido de computadora, ruido de ventilador, ruido tonal, ruido periódico, ventilador de computadora, control activo de ruido.

 

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