Noise cleaner technology can be regarded as a separate area in speech technologies. A beep in phonograms or in transmission and sound recording channels differs from the original one. This is because firstly, there are noises and distortions in listening signal that adversely affect the quality and intelligibility of speech, and secondly, it depends on the characteristics of our hearing. In this regard, quite often there is need for special treatment, or noise cleaner system of sound signal.
In some cases, poor quality of the resulting record creates certain difficulties for the information decryption. The reasons for this are failed or inept choice and usage of transmission and record medium of audio information and objective difficulties and even impossibility of obtaining high-quality “clean” audio recording in certain specific circumstances.
While processing the record technician faces the following challenges:
- Carry out maximum possible speech cleaning in order to remove noise and distortions
- Examine sound recordings
For any operation with low-quality audio recordings there is need for technically competent trained professionals and the various technical means.
During the examination it is usually required to establish occurrence of traces of deliberate assembly or recording backup; determine the type or to identify a specific instance of recording device; state the recording circumstances, method, environmental conditions, location of sound recording facilities, type of noise source, and so on; establish identity or voice difference in this (disputed) recording with voice which sample is in another (relative) audio record. In some cases, it’s required to determine speaker’s distinctive features in the speech recording (examples, gender, age, place of birth, occupation, diseases, etc.).
Facilities and technologies of noise cleaner ensure bringing quality and intelligibility of the speech signal to a level acceptable to its comfortable listening and understanding preserving important properties and characteristics of the speaker and circumstances of obtaining information, which is a very important factor.
Noise cleaner technology of speech signals is classified by type of distortion:
- BABBLE NOISE - crowd noise cancellation technology
- MUSIC NOISE - music noise cancellation technology
- NONSTATIONARY NOISE - transient noise cancellation technology
- PULSE NOISE - impulsive noise cancellation technology
- TONAL NOISE - tonal noise cancellation technology
- WIDEBAND NOISE - broadband noise cancellation technology
- GSM HINDRANCE - noise pickup cancellation technology of cellular telephones
- CLIPPING - signal clipping
- REVERBERATION & NOISE – reverberation
Speech sound recording is widespread as a security tools technique in various areas of human activity. In particular, verbal directions and negotiations of air crews and large vehicles, personnel of complex technical objects, telephone conversations of various medical, emergency and law-enforcement services, commercial organizations are recorded. In some cases the fixation of speech and of other acoustic signals in industrial areas is required. Explicit and hidden means of recording are used for logging of operational information during negotiations, meetings, lectures and accident prevention actions. In some areas of human activity precise deciphering of recording speech is essential.
