Study on the Selection of Specific Filters for Enhancement of Recorded Speech for Speaker Identification

ABSTRACT

Understanding the noise characteristics for finding appropriate filtering technique/s so as to obtain sufficiently clear speech samples for Speaker Identification, is one of the challenging tasks in Forensic Acoustics. Speaker’s idiosyncratic speech should not be affected when the noise reduction is carried out; otherwise, Speaker Identification becomes highly erroneous. We have collected fifty noisy speech samples reported to be recorded in different modes from actual crime cases received in the laboratory. The samples are analyzed after subjecting to various filtering techniques and compared with the clear speech mixed with the noise collected from non-speech portion. Distortion levels on the speech are studied at various stages of application of filters in terms of SNR and Speaker Specific Information. Retaining the Speaker Specific Information as primary concern of our study, the limitation of filtering techniques depending on the characteristic and intensity level of noise is worked out for noisy speech samples. Subsequently a statistical study is also conducted. Listening tests were conducted to ensure that the perceptual features of the original noisy speech are preserved while applying filters. This work demonstrates the efficiency of Noise reduction filters in improving SNR and their controlled applications for preserving Speaker dependent features depending on the various noise characteristics embedded on speech samples.