Real-time System For Virtual Bass Enhancement Based On DSP

With a rapid development of science and technology today, large kinds ofportable mediaequipments and electronic products have penetrated into all fields of people’s life. Smallloudspeakers as a indispensable sound-reproduction device, benefitted from the features ofsmall size and low power consumption, have gained a wide application market. But due to thephysical restrictions such as the size of diaphragm and cavity structure, these small speakershave an inherent poor ability in reproducing acoustically low frequencies. Thus, they alwayscan’t meet the people’s pursuit and enjoyment for the deep and vigorous bass sensation.Since the phenomenon has been found in the psychoacoustic field that a low-frequencybass perception can be virtually rendered using its harmonic components, the tech calledvirtual bass enhancement has been become a research hot spot, of which the MaxxBass andVB Phase Vocoder algorithm are the most representative. On the basis of these algorithms,Wu Donghai proposed a virtualbass enhancement algorithmbased on harmonic control underthe guidance of his director in2012. This algorithm took into account of the results about therelationship between the timber and harmonic components chose a harmonic proportion moreclosed to the real bass musicality perception and adopted a numerical calculation model tocontrol the loudness reduction, so the bass effect is obvious. However, it has a highcomplexity, large amount of calculation and a very slow speed as it processed with the wholesignal samples, so this algorithm didn’t realize the real time processing.In order to promote the practical application and be able to realize the real-time bassenhancement processing when replaying music at the same time, this paper first introducedthe theoryofbass enhancement algorithm, taking its feature into account, thenproposed somemodificationwith simplification combined with a block-based audio real-time processing tech.At the second part, this thesis presented a DSP-based general system design as well asimplementation scheme for real-time audio signal processing and then a successfultransplantation of the modified algorithm to a low-priced DSP development board withTMS320VC5502as its core. Thus, we eventually verified the feasibility of the algorithm andrealized signal acquisition, replay and real-time bass enhancement processing at the sametime.Limited bycalculation accuracyas well as the processing speed and storage capacity, thereal-time algorithm has changed a lot especially for simplificationand thus resulted in a bit ofdecline as to the effect suchas the timber and loudness in comparisonwith the none real-time algorithm in Matlab on a PC. To evaluate the bass-enhancement effects, this paper conductedsome subjective listening experiments at the last part. Results show that: the real-time virtualbass enhancement systm can obviously improve the bass display effect of the small-sizedspeakers with very little sound quality damage.