| 31. |
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| 32. |
- Claesson, Ingvar, et al.
(author)
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Cancellation of Humming GSM Mobile Telephone Noise
- 2003
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Conference paper (peer-reviewed)abstract
- A sometimes annoying problem in the most internationally widespread cellular telephone system, the GSM system, is an interfering signal generated by the switching nature of TDMA cellular telephone system. A humming noise originating from the speech frames, equivalent to 160 samples of data corresponding to 20 ms at 8 kHz sampling rate is sometimes clearly audible. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are Notch Filtering, which is performed on a sample-per-sample basis, and Speech Frame Noise Cancellation, which is an alternative method employing correlators and subtraction, similar to Active Noise Control.
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| 33. |
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| 34. |
- Claesson, Ingvar, et al.
(author)
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Car Performance of an Adaptive Microphone Array
- 1992
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Conference paper (peer-reviewed)abstract
- Hands free input of mobile telephones is often almost impossible due to the noise situation in the car and the channel quality. The authors present a method to enhance the quality using an adaptive microphone array. Measurements show an improvement of the input with approximately 10 dB. Tape results are available for subjective evaluation.
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| 35. |
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| 36. |
- Claesson, Ingvar, et al.
(author)
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Device and a method for preventing or reducing vibrations in a cutting tool
- 2007
-
Patent (pop. science, debate, etc.)abstract
- An arrangement for reducing vibrations in a tool holder (4) with a cutting tool (3) and has a vibration sensor on the tool holder (4) that is connected to a guide unit (11). The tool holder (4) has further two piezo-electric actuators 14 and 15.Under the influence of the vibration sensor (9), the guide unit (11) provides an electric alternating current that is actively guided over time so that the actuators movably affect the tool holder (4) to reduce the vibrations in this. To also be able to dampen transients in the tool holder (4) this is movably connected with a passive dampening arrangement that is independent of the guide unit (11) and that is based on the principle of a springing (8) suspended mass (7). The invention also relates to a method for reducing vibrations. The vibrations in the tool holder are sensed and a corresponding signal is provided to a guide unit that over time provides actively guided signals to the actuators. The tool holder is also passively influenced by a dampening arrangement that is independent of the guide unit.
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| 37. |
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| 38. |
- Claesson, Ingvar
(author)
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FFT i ett historiskt perspektiv
- 1997
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Conference paper (peer-reviewed)abstract
- Några nedslag i Fouriertransformens historia och FFT:ns ursprung från 1805 och framåt behandlas i denna populära betraktelse. Vi stannar upp ett slag hos Gauss, funderar över vad han gjort för oss ingenjörer och vi avslutar med en del praktiska konsekvenser och tips som är aktuella idag.
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| 39. |
- Claesson, Ingvar
(author)
-
FFT i ett historiskt perspektiv
- 1997
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In: SVIB vibrationsnytt. - Täby : Svenska vibrationsföreningen (SVIB). - 0281-6830. ; 14/15:1, s. 11-15
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Conference paper (peer-reviewed)
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| 40. |
- Claesson, Ingvar, et al.
(author)
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GSM TDMA Frame Rate Internal Active Noise Cancellation
- 2003
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In: International Journal of Acoustics and Vibration. - : Int. Inst. Acoustics and Vibration, USA. - 1027-5851 .- 2415-1408. ; 8:3, s. 159-166
-
Journal article (peer-reviewed)abstract
- A common problem in the world's most widely-used cellular telephone system, the GSM system, is the interfering signal generated by the switching nature of TDMA cellular telephony in handheld and other terminals. Signals are sent as chunks of data, speech frames, equivalent to 160 samples of data corresponding to 20 ms at sampling rate of 8 kHz. This paper describes a study of two different software solutions designed to suppress such interference internally in the mobile handset. The methods are 1) notch filtering, which is multiplicative in frequency, and 2) subtractive noise cancellation, which is an alternative method employing correlators. The latter solution is a straigtforward, although somewhat unorthodox, application of "in-wire" active noise control. Since subtraction is performed directly in the time domain, and we have access to the state of the mobile, it is also possible to consider a recurring pause in the interference caused by the idle frame in the transmission, when the mobile listens to other base stations communicating. More complex control algorithms, based on the state of the communication between the handset and the base station, can be utilised.
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