Laura Laaksonen

Occupational voice complaints and objective acoustic measurements-do they correlate?

To enable the development of appropriate diagnostics and treatment for occupational voice disorders, this study addresses connections between subjective voice complaints and objective observations. The subjects of this study were 24 female customer advisors, who mainly use the telephone during their working hours. During one working day, at four different times, speech samples covering 20 minutes of telephone conversation by the customer service advisors (CSAs) were recorded. In addition, the CSAs filled in a questionnaire (visual analogue scale) concerning their voice problems. To represent the vocal symptoms three variables were used: vocal fatigue, hoarseness and a general sum-variable. A 5-minute sample was taken from recordings for further analyses. This included fundamental frequency, sound pressure level, alpha ratio (the ratio between the spectral energy below and above 1000 Hz) and number of vocal fold vibrations. In the objective acoustic measurements, it was found that fundamental frequency (F0) rose significantly during the working day. Also the self-reported voice symptoms increased significantly during the working day. However, correlations between vocal symptoms and acoustic measures were not found.

Evaluation of an Artificial Speech Bandwidth Extension Method in Three Languages

Quality and intelligibility of narrowband telephone speech can be improved by artificial bandwidth extension (ABE), which extends the speech bandwidth using only information available in the narrowband speech signal. This paper reports a three-language evaluation of an ABE method that has recently been launched in several of Nokias mobile telephone models. The method extends the speech bandwidth to frequencies above the telephone band by first utilizing spectral folding and then modifying the magnitude spectrum of the extension band with spline curves. The performance of the method was evaluated by formal listening tests in American English, Russian, and Mandarin Chinese. The results of the listening tests indicate that ABE processing improved the subjective quality of coded narrowband speech in all these languages. Differences between bandwidth-extended American English test sentences and their original wideband counterparts were also evaluated using both an objective distance measure that simulates the characteristics of human hearing and a conventional spectral distortion measure. The average objective error was calculated for different categories of speech sounds. The error was found to be smallest in nasals and semivowels and largest in fricative sounds.

Neural Network-Based Artificial Bandwidth Expansion of Speech

The limited bandwidth of 0.3-3.4 kHz in current telephone systems reduces both the quality and the intelligibility of speech. Artificial bandwidth expansion is a method that expands the bandwidth of the narrowband speech signal in the receiving end of the transmission link by adding new frequency components to the higher frequencies, i.e., up to 8 kHz. In this paper, a new method for artificial bandwidth expansion, termed Neuroevolution Artificial Bandwidth Expansion (NEABE) is proposed. The method uses spectral folding to create the initial spectral components above the telephone band. The spectral envelope is then shaped in the frequency domain, based on a set of parameters given by a neural network. Subjective listening tests were used to evaluate the performance of the proposed algorithm, and the results showed that NEABE speech was preferred over narrowband speech in about 80% of the test cases

Artificial bandwidth expansion method to improve intelligibility and quality of AMR-coded narrowband speech

Speech quality suffers from the limited bandwidth of cellular telephone systems, making it sound muffled. In addition, intelligibility is degraded due to missing higher frequency components. The proposed enhancement system is designed to improve both intelligibility and quality of narrowband speech by expanding the bandwidth and creating new spectral components to high frequencies in the receiving end of the transmission link. The algorithm can be used together with conventional narrowband speech codecs and it is designed to be robust in different noise conditions. In addition, the computational load of the algorithm is reasonable.

Development, evaluation and implementation of an artificial bandwidth extension method of telephone speech in mobile terminal

Artificial bandwidth extension methods aim to improve the quality and intelligibility of narrowband telephone speech by adding new, artificially generated spectral content to the highband of the received voice signal. The development cycle of an artificial bandwidth extension method from the initial idea to the implementation in a mobile terminal is discussed in this paper. Developing the algorithm in the Matlab environment was the first step in the process. The method was then evaluated in formal listening tests and simulations to verify its performance in different scenarios. Finally, the utilization of this technology in a product included its DSP implementation combined with the acoustical design of the user terminal.

Conversational quality evaluation of artificial bandwidth extension of telephone speech

Artificial bandwidth extension methods have been developed to improve the quality and intelligibility of narrowband telephone speech and to reduce the difference with wideband speech. Such methods have commonly been evaluated with objective measures or subjective listening-only tests, but conversational evaluations have been rare. This article presents a conversational evaluation of two methods for the artificial bandwidth extension of telephone speech. Bandwidth-extended narrowband speech is compared with narrowband and wideband speech in a test setting including a simulated telephone connection, realistic conversation tasks, and various background noise conditions. The responses of the subjects indicate that speech processed with one of the methods is preferred to narrowband speech in noise, but wideband speech is superior to both narrowband and bandwidth-extended speech. Bandwidth extension was found to be beneficial for telephone conversation in noisy listening conditions.

Conversational Evaluation of Speech Bandwidth Extension Using a Mobile Handset

The quality of narrowband telephone speech can be improved by artificial bandwidth extension. So far, bandwidth extension methods have been evaluated with objective measures and subjective listening-only tests, whereas realistic conversational evaluations have been rare. This article presents a conversational evaluation of two bandwidth extension methods in comparison with narrowband and wideband references. The evaluation was carried out using a mobile handset with a wired earpiece and microphone both in silence and in simulated street noise. The results indicate that speech processed with one of the bandwidth extension methods was preferred over narrowband speech.

Conversational evaluation of artificial bandwidth extension of telephone speech using a mobile handset

Artificial bandwidth extension methods have been developed to improve the quality and intelligibility of narrowband telephone speech. Bandwidth extension methods have typically been evaluated with objective measures or subjective listening-only tests, whereas realistic conversational evaluations have been rare. This paper presents a conversational evaluation of two bandwidth extension methods together with narrowband and wideband speech. The evaluation was performed using a mobile handset with a wired earpiece and microphone both in silence and in simulated street noise. The results indicate that one of the evaluated bandwidth extension methods was significantly preferred over narrowband speech in silence. The results also suggest slight preference for this bandwidth extension method over narrowband speech in street noise. True wideband speech was considered superior to bandwidth-extended and narrowband speech especially in silence.

Binaural artificial bandwidth extension (B-ABE) for speech

Efficient teleconference system can be created by extending the speech bandwidth and using spatial audio. If wideband speech transmission was not supported as such, an alternative way to extend the bandwidth is by exploiting an artificial bandwidth extension (ABE) algorithm. In such methods the audio bandwidth is extended in the receiving end, without any transmitted extra information. When considering spatial audio it should be noted that ABE methods have been developed for monaural signals and they cannot be applied as such to binaural signals due to a possible mismatch of binaural cues in the created frequency range. In this paper binaural ABE, B-ABE, is proposed. Subjective listening tests were used to evaluate the proposed method. The results showed that the localization information is preserved well in B-ABE processing.