#Study about filter and hearing aids circuit
Day 1: What is filter?
It is sometimes desirable to have circuits capable of selectively filtering one frequency or range of frequencies out of a mix of different frequencies in a circuit. A circuit designed to perform this frequency selection is called a filter circuit, or simply a filter. A common need for filter circuits is in high-performance stereo systems, where certain ranges of audio frequencies need to be amplified or suppressed for best sound quality and power efficiency. You may be familiar with equalizers, which allow the amplitudes of several frequency ranges to be adjusted to suit the listener's taste and acoustic properties of the listening area.Example:
Television signal splitter consisting of a high-pass filter (left) and a low-pass filter (right). The antenna is connected to the screw terminals to the left of center.
Day 2: Ideal filter types
1-Lowpass: Attenuates frequencies above cutoff frequency, letting frequencies below cutoff( fc) through;
2- Highpass: High pass filters stops low frequencies, letting higher frequencies through;
3-Bandpass: Letting through only frequencies in a certain range,
Day 3: Ic filter circuit
This be the circuit filters 10KHz low size frequencies s use IC op-amp the highly popular number uA741. By this circuit convenients for to apply to input and output of the circuit changes analog signal be digital or the circuit changes digital signal be digital. In sound system of digital for synthetic the voice or music give for make wave form output the smooth. And press the noise that happen at output. When small-sized signal was managed with decrypt linear the size is 8 bit.
Day 4: Understanding Sound
The Decibel (dB) is the unit of measurement used in sound systems. A Decibel (dB) describes a ration between two quantities expressed as a logarithm. Logarithms are used because our ears hear differences in loudness as a Log function. In simple terms, 3 dB represents twice as much power, and 10 dB represents 10 times as much power
- 2 * power = 3 dB
- 4 * power = 6 dB
- 8 * power = 9 dB
- 10 * power = 10 dB
Day 5:
Frequency Range of the Human Voice
A voice frequency (VF) or voice band is one of the frequencies, within part of the audio range, that is used for the transmission of speech. The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about:
#Voice range covers 300 Hz to 3500 Hz
#Most energy concentrated below 1000 Hz
#owels have most of their energy below 1000 Hz
#Vowels contain the "power and impact of the voice"
#Consonants have most of their energy above 1000 Hz
#Consonants are responsible for intelligibility
#Harmonics in voice can go above 3500 Hz
#Poor high frequency response reduces intelligibility
