Telecommunications Industry Association TR41.3.12-11-08-006-L Document Cover Sheet Project Number PN-3-XXXX (leave blank if unknown or not applicable) Document Title Evaluation of Answering machine voice quality in remote access mode. Source Embarq Local Access Solution Development 6050 Sprint Pkwy Overland Park, KS-66251 Contact Amar Nath Ray Phone: 913-794-6691 6050 Sprint Pkwy Fax: 913-794-0412 Email: email@example.com Overland Park, KS-66251 Phone: 913-794-6430 C.V. Chakravarthy Fax: 913-794-0412 EMBARQ Email:Cadathur.Chakravarthy@mail.sp 6050 Sprint Parkway rint.com Overland Park, KS, 66251 Distribution TR-41.3.12 Intended X For Incorporation Into TIA Publication Purpose of For Information Document Other (describe) - (Select one) The document to which this cover statement is attached is submitted to a Formulating Group or sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of which provisions are hereby incorporated by reference. Telecommunications Industry Association TR41.3.12-11-08-006-L Abstract: The voice qualities of several digital answering systems connected to real voice network were checked remotely using a digital speech level analyzer. The mean opinion scores (MOS) as measured by this test were found to be lower than PSTN voice quality. Test set up: The following diagram shows the experimental set up used for this test. Remote access DTAM voice quality measurement set up Send speech sinal Telephone DSLA Network Retive store signal Telephone with DTAM Test set up sequences: 1. DSLA calls the DTAM 2. DTAM goes off-hook after three rings 3. DSLA sends message after waiting a certain period of time (for DTAM to send OGM and get ready for recording messages) 4. DSLA goes on-hook and waits for specified time 5. DSLA calls DTAM again 6. DSLA waits for a certain period of time (for DTAM to send OGM) and sends remote access code 7. DSLA waits a certain period of time and sends DTMF code for retrieval of message 8. DSLA waits for some time (critical as discussed later in this document) and start PAMS measurements 9. DSLA goes on-hook Telecommunications Industry Association TR41.3.12-11-08-006-L The screen shot given below is an example of the results as measured by the Perceptual Analysis Measurement System (PAMS). The results shows that the end to end remote access voice quality is lower than that of PSTN as shown later in this document. The parameters for the measurement above are given below. The time delay of 508ms (5ms for DSLA) was the minimum out of the measurements made. Listening Effort – 4.11 Listening Quality – 3.63 Time Offset – 513 ms Time Offset Confidence – 67% The table below is showing the parameter levels for speech quality measurements with five DTAMs from various vendors. Sample number Listening effort Listening Quality One way delay A 3.7 3.2 612 ms B 4.0 3.5 520 ms C 4.1 3.6 508 ms D 4.0 3.4 575 ms E 3.7 3.4 565 ms Telecommunications Industry Association TR41.3.12-11-08-006-L The time duration after the remote access code followed by the message playback code is crucial for good MOS score. The table below shows the degradation of the MOS scores with the time duration for a specific device. Time duration Listening Effort Listening Quality 1.25 4.0 3.5 1.5 4.0 3.5 2 4.0 3.6 2.25 4.1 3.7 2.5 3.9 3.4 3.0 2.5 1.0 The PAMS screen shot as given below was measured by the same DSLA system. The PAMS chart as shown above is giving the best results for a PSTN call using the same line. Note: The signal level of the reference signal is important for measuring the MOS scores. Please look at the message from Nick Fox of Malden, UK. Gentlemen, Because the test takes place in two phases, PAMS needs to know which files to compare with the replayed speech. "Generating" speech at -99dBm is just a Telecommunications Industry Association TR41.3.12-11-08-006-L method of achieving this. If the level is increased, the resulting signal gets mixed with the replayed speech and thus the score is degraded. I hope this makes sense. With best regards, Nick ________________________________________ From: Ray, Amar N [LTD] [mailto:Amar.Ray@embarq.com] Sent: 02 November 2006 21:31 To: Nick Fox Cc: Ray, Amar N [LTD]; Chakravarthy, C V [LTD] Subject: RE: DSLA Nick: Me and CV, we have question about the sequence that you have used in the TAM files. Why you used -99dBM signal level in that file? FYI, we have tried with signals higher than -99dBM (-40 and -20) and found degraded PAMS scores. Thanks, Amar/CV Recommendation: More tests are in progress. The committee will be informed with more results later on to make specific recommendations for setting the requirements on DTAM’s remote access speech qualities. At this point, a MOS level of 3.4 is suggested.
Pages to are hidden for
"Standards Project"Please download to view full document