Saturday, February 23, 2008

Editing the audio files

I was not able to attend the actual talk being recorded but from all accounts there were no problems with the actual recording. The speaker arrived early so it was possible to pre-test that everything was working. Fortunately the microphones that we had left set up at the dress rehearsal on the Friday were at the right height for the speaker and therefore did not need adjusting - so luck was on our side there. We were also very fortunate to have a speaker who was aware that this was an experiment and did not mind being confronted with recording equipment. He was also an experienced speaker.

Both the recordings made provided clear audio files. The recording made using the digital recorder and the lapel microphone, as well as recording the voice of the speaker clearly, also picked up the voices of the people introducing and thanking the speaker reasonably clearly. The voices of people asking questions during question time were also audible even though some of these people were sitting near the back of the room. The recording made via the microphone connected directly to the computer clearly picked up voices speaking directly into it. No attempt was made to record question time using this set up.

At the RHSV I did a quick spot check of both audio files and then transferred the audio files to a USB flash drive to transfer to my computer at home.

The recording of the lecture recorded directly to the computer using the Audacity program had been saved as Audacity Project Files. This creates two sets of files both containing the name under which the project was saved - a data folder containing the audio file broken down into segments and the full .aup file. When transferring the Audacity files from one computer to another, both sets of files need to be transferred. I had transferred only the folder with the segments so I could only work with 12 second segments of the tape. As an experiment I imported a number of these files into Audacity and combined them into one file but was not prepared to do that for a 48 minute recording. Still I proved to myself it could be done and in future I will remember to save both the files when transferring Audacity files. When next at the RHSV I collected the other file and was then able to work with the complete file.

The recording of the lecture recorded on the digital recorder was saved as a MP3 file. When I tried to import this file into Audacity on my lap top at home I was not able to open the file as it was 67MB. I used the program, MP3Tweak -, to compress the file and was then able to open it in Audacity.

Originally we had not intended to include questions but as they had recorded so clearly I decided to use them as a separate file. Although the voices of the questioners were reasonably clear I was able to enhance the voice of each speaker to make it louder.

I did not edit the actual lecture as the recording was clear and the aim of the exercise was to reproduce a recording of a talk given on a particular night. If there had been large pauses or problems during the talk I could have removed them quite easily. I did however edit the introduction to the talk - only using the sections relating directly to the speaker and the topic.

After going through both recordings of the talk I was able to produce two files. The first contained a short introduction followed by the talk - 48 minutes. The second file contained question time and the vote of thanks to the speaker - 20 minutes.

The recording of the lecture itself used was the audio files made via the microphone directly to the computer but the recording made from the digital recorder via the lapel microphone could also have been used. The latter method provided the audio files for the questions.

Each audio file was exported from Audacity as an MP3 file and then compressed using MP3Tweak. The first file was 11.2MB and the second file 5.2MB.

A number of sites on the Internet provide information about using Audacity. Audacity Tutorial is a good place to start and there is also Audacity Wiki which provides information about the software.

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