# 0.10 Jbs2060-a player piano simulator  (Page 13/17)

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Listing 22 shows a for loop that is used to compute the amplitude at the current time in the current sample including the possibility oftwo or more keys being pressed. When two or more keys are pressed simultaneously, the amplitude of the output is computed as the sum of theamplitudes of the individual keys. This code shouldn't require an explanation beyond that provided by the embedded comments. Note that the name of the key isused to extract the frequency for that key from the Hashtable object that was created by the method named getPiano that was called in Listing 19 .

Listing 22 . Process each piano key that is pressed.
```for(int element = 1;element<array.length;element++){ //Iterate on the piano keys defined in the array.//Get the name of the next key and make sure that it is upper-case. String noteName = array[element].toUpperCase(); try{//Use the noteName and get the corresponding frequency from the // hashtable. Note that results are retrieved from the list as// type Object and must be cast to the correct type. freq = (double)piano.get(noteName);}catch(java.lang.NullPointerException ex){ ex.printStackTrace();System.out.println("noteName: " + noteName); }//end catch//Compute the amplitude for this note at this time and add it to// the sum unless it is a musical rest. if(!noteName.equals("X")){//This is not a musical rest. sum += Math.cos(2*Math.PI*(freq)*time);}//end if //Go back to the top of the loop and get the next key from the// array, if any. }//end for loop```

## Use a scale factor to shape the note

If you press a key on some electronic keyboards and hold the key down, the sound intensity will remain constant with time. However, if you press a pianokey and hold it down, the sound intensity decreases over time. The code in Listing 23 attempts to achieve that same effect.

Listing 23 . Use a scale factor to shape the note.
```scaleFactor = gain*((beats*audioParams.sampleRate/beatsPerSec) - cnt) /(beats*audioParams.sampleRate/beatsPerSec);//Scale the amplitude value and put it into the output array. byteBuffer.putShort((short)(scaleFactor*sum));//Go back and compute the next sample values for this set of keys // until the note duration is satisfied.}//end for loop //Go back, retrieve, and process the next set of keys for a given// duration value. }//end while}//end makeMusic method```

At this point in the creation of the audio sample, the amplitude values for all the keys that were pressed simultaneously have been added together.The resulting amplitude value is scaled so that each note has a maximum amplitude at the beginning and a zero amplitude when the duration has expired. Alinear scale factor is used to accomplish this.

The remaining code in Listing 23 shouldn't require an explanation.

Listing 23 ends the for loop that began in Listing 21 , ends the while loop that began in Listing 20 , and signals the end of the makeMusic method.

#### Questions & Answers

can someone help me with some logarithmic and exponential equations.
sure. what is your question?
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
a perfect square v²+2v+_
kkk nice
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
rolling four fair dice and getting an even number an all four dice
Kristine 2*2*2=8
Differences Between Laspeyres and Paasche Indices
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
is it 3×y ?
J, combine like terms 7x-4y
im not good at math so would this help me
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
how do you translate this in Algebraic Expressions
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
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preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
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Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
can nanotechnology change the direction of the face of the world
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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