This is two part exercise. In first part you will listen to the quality

VoIP Exercise

This is two part exercise. In first part you will listen to the quality of speech of five voice coding standards. You will compare the quality of different codecs (http://www.data-compression.com/speech.shtml#demo) and give your rating from 1 to 5. One is the poorest quality and 5 is the best quality. Fill out the rating column in table 1-1.

Table1-1

In the second part, we will be examining the use of voice telephony over the Internet and match the quality of voice with the standard voice scheme (From Table1-1). Specifically, we will be using Skype to make PC to PC connections and reporting on the perceived quality of the calls. You will be required to call at least two students or friends and assess the quality of the voice call. Please make your own arrangements for who and when you will call. Please fill out all the columns of table 2-2. I have completed the first row as an example. Use voice scheme from Table1-1.

Table2-2

The Skype software is free and there are no charges as long as you call from one PC to another PC. Skype charges a fee for making calls into the conventional POTS telephone system.

The quality of VoIP calls is strongly dependent on the bandwidth of your Internet connection. The best quality will be obtained with a wideband connection. If you are using dial up, your call quality may be poor. Please make sure you write down the type of Internet connection you are using in the box in the table2-2.

Side Note: Personally I use Vonage, which is another Internet VoIP service provider. I believe Vonage has better voice quality than Skype, but Skype is getting better. However, the Vonage service is not free; therefore, I did not use it for this exercise. Please note that someone best quality sound is other person worst quality sound. These sound schemes are very close and it is difficult to differentiate just on the basis of sound. In real life lot of samples are tested on different bandwidth and compression ratios and most economical sample is selected.

Skype Quality Exercise

Download the Skype software and install it on your PC per the directions below. For this exercise, you call one other student in your group or a friend and assess the quality of the call.

I have provided a URL that discuss voice quality. You will be required to report on the quality of at least two calls including the Absolute Category Rating (ACR) Test, which is discussed in the article below. It uses a scale of 1 to 5 on overall quality.

Tech Note: Voice Quality Measurement

http://www.tmcnet.com/tmcnet/articles/2005/voice-quality-measurement-voip-alan-clark-telchemy.htm

Detailed Instructions

1. Download and install Skype. http://www.skype.com/intl/en/download/skype/windows/. You may have to click on "International English" at the bottom of the Web page to get the English page. Be sure and select the free version.

2. Although you can use the microphone and speakers in your PC for this lab, it is recommended that you borrow or procure a set of head phones with a microphone, which can be purchased for under $10. Head phones provide better quality than speakers.

3. Contact your partner and arrange times for calls.

4. Make your Skype call and then fill out the Table 2-2 with your assessment of the Skype call.

5. Also compare the quality of the various compression schemes from http://www.data-compression.com/speech.shtml#demo

6. Answer the question regarding whether you would use VoIP.

Please submit Table1-1, and Table2-2 thru Skype assignment folder.