Frequency compression

Fairbanks et al., 1954] Fairbanks, G., Everitt, W., and Jaeger, R. (1954). Method for time or frequency compression-expansion of speech. IEEE Trans. Audio and... 

Low frequency compressibility modulus in the SmA phase of 8CB is temperature dependent and is 2 lO N/m [11]. However, the scattering of the value of B is comparable to its mean value, which is probably due to the not well defined radius of the AFM tip (adsorption and desorption of molecules). Moreover the shape of the tip-end is spherical only in first approximation. To obtain more precise measurements of B, well defined and somewhat larger spherical particles (J w 100 nm) should be used instead of a sharp AFM tip. 

A factor which has to be taken into consideration, especially in the MBE growth of layered systems, is the influence of effective pressure and strain on the vibronic properties of the semiconductors. Strain effects arise because of the differences in the lattice constants. This difference leads to a distortion of the crystal lattice, which causes a shift of the bandgap energy and, thus, directly affects the optical properties of the layered systems. Therefore, it is important to investigate strain effects quantitatively. The compression (expansion) of the lattice constants by strain effects is equivalent to a change in the interatomic distances and therefore leads to a shift of the LO-phonon frequency. Compressive (tensile) strain leads to a blueshift (redshift) of the phonon wave number. The amount of this shift is proportional to the strain. Strain shifts can mask confinement shifts or compositional shifts. Therefore, it is necessary to separate the strain-induced part of the shift from the other parts. In addition to the dependence on the difference in the lattice constants, the strain shows also a dependence on the thickness of the layer. The strain increases with increasing layer thickness up to a critical thickness. From this thickness onward, the strain decreases because of the formation of misfit dislocations. The appearance of misfit dislocations can be observed in the Raman spectra as an increase in the intensity of the symmetry-forbidden TO-phonon peak as well as a broadening of the LO-phonon peak. 

Improving Low Pass Filtered Speech Intelligibility Usii Nonlinear Frequency Compression with Cepstrum and Spectral Envelope Transformation... 

Keywords— Frequency compression, spectral envelope, low pass filtered speech, speech intelligibility, h h frequency hearing loss. 

In this paper, we describe a method to nonlinearly compress the high frequency component of speech to the lower frequency region without affecting the speech intelligibility. The frequency compression process can be performed by transforming the estimated spectral envelope using nonlinear frequency compression method. 

Nonlinear frequency compression compresses the frequency of the input signal and simultaneously preserves the speech feature such as formant ratio. The compression can be performed by applying a nonlinear frequency compression function to the input signal frequency [3, 4 6]. Higher frequency component will require more compression compared to the lower frequency component. The frequency compression function is given by... 

The block diagram for the nonlinear frequency compression method used in this work is as shown in Figure 3. 

Fig. 3 Proposed nonlinear frequency compression system block diagram...

Fig. 4 Frequency compression factor from setting 1 to 25 and its maximum output frequency show that the maximum frequency become constant as the frequency compression factor increases...

Fig. 7 Low pass filtered, frequency compressed output signal and its spectrogram. The high frequency components at around 0.4 and 0.9 s are compressed to lower frequency region below 2 kHz...

Fig. 8 Input and output frequency of the nonhnear frequency compression with frequency compression factor of 4 to produce the maximum output frequency of 2 kHz...

In this work, we afforded a method that used the nonlinear frequency compression to improve the speech inteliigi-bility for the person with high frequency hearing loss. After... 

Improving Lx)w Pass Filtered Speech Intelligibility Using Nonlinear Frequency Compression... 

We also conducted informal listening test to evaluate the speech intelligibility of the low pass filtered and frequency compressed output signal. The listening test result showed that the output speech was improved compared to the low pass filtered input signal. This result confirmed that the speech intelligibility has being improved. 

Bohnert, A., Nyffeler, M, Keilmann, A. (2010) Advantages of a nonlinear frequency compression algorithm in noise. Eur Arch Otorhino-laryngol 267 1045-1053... 

Ultrasonics Welding employs high frequency compressive vibratory energy, either at 15kHz,... 

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