Can students get useful feedback on their speaking from NotebookLM?

The short answer is, "Yes, they can." But, students may need ideas for how to design a prompt that will produce feedback that will encourage and help them.

This is the prompt I have experimented with:

Act as a sympathetic supportive teacher of English as a Foreign Language offering helpful advice about how to correct and improve the student’s recordings. Pay particular attention to errors that are repeated in various recordings. Make sure the language used will be understood by the learner who produced the recordings. The names of the files show when the recordings were made. So 2014 is the year, the next two numbers are the month and the following two are the day.

I used this as a  'Create your own' prompt for a report on a sequence of transcripts and mp3 files of recording made by the student over a term. There were 49 sources in all.

Here is the introduction to the report:

Feedback on Your English Recordings: Great Progress and Key Areas for Improvement

Hello!

First and foremost, I want to say a huge well done for all the hard work and dedication you've put into making these recordings. It takes courage to practice speaking so consistently, and your effort is clearly paying off. The purpose of this feedback is to offer some friendly, supportive guidance on a few common patterns I noticed. Think of these as small adjustments that can make a big impact on your clarity and confidence.

We'll look at three main areas: Pronunciation, Grammar, and Vocabulary. After that, I want to highlight your many strengths, because you are doing so much right! Finally, I'll offer a few simple tips for what to practice next. Please remember that making mistakes is a normal and very important part of learning a language. Every error is an opportunity to learn, so be proud of the progress you're making.

And towards the end: 

4. Your Strengths: What You Are Doing Well

I want to be very clear: your progress is excellent, and you should be incredibly proud of your speaking ability. You have many strengths that shine through in your recordings.

Analysis of Key Abilities

• Excellent Summarizing Skills: You have a real talent for listening to or reading information and then explaining the main ideas clearly and accurately. Your summaries of the chef Steve Anderson and the BBC experiment with the chess players were fantastic. For example, you didn't just retell the story; you correctly identified the most important details, like how the chess player who ate protein played better and how chocolate was used to reduce aggression in nightclubs. This shows strong comprehension skills.

• Great Fluency and Confidence: You are not afraid to speak! You confidently express complex opinions and ideas on a wide range of topics, from food and family to work and money. The detailed conversation about whether men or women are better cooks was a wonderful example of this. You confidently shared your opinion, backed it up with examples of famous male chefs like Ferran Adrià, and respectfully disagreed with your partner. This ability to engage in a complex debate is a sign of great fluency.

• Wide Vocabulary Range: You already use a broad and impressive range of vocabulary. You can talk about many different subjects and use specific words related to food, personality traits, family relationships, and work. This is a huge strength.

5. Summary and Next Steps

Overall, you are a confident and capable speaker who is making wonderful progress. By fine-tuning a few small areas in pronunciation and grammar, you can make your already strong communication skills even more effective.

Here's a link to the whole report, which I copied into a Google Doc.

I also experimented with using prompts in the Chat.

1. The names of the txt files show when the recordings were made. So 2014 is the year, the next two numbers are the month and the following two are the day. Can you detect any changes in the speakers English as the dates of the transcripts advance?
2. From the selected transcripts can you offer some help to lidia about her English? 
3. What did Lidia talk about in the selected mp3 files? 
4. What errors did you detect in the selected mp3 files?
5. Can you make a list of the transcripts and recordings in order with a suggested title?
6. Can you add a column with a grade out of 5 for spoken communication when this would be approrpiate?
7. Can you make a graph showing the ones with grades and eliminating duplicates?
8. Can you make a visual representation of these grades plotted against dates?

This is a link to the whole Notebook

I asked for a grade for the report, or at least the first 1000 words of it, from Text Inspector and Pearson's Text Analyzer and these showed the report was pitched a bit above the B1 student's level.

Text Inspector    C1     62%

Text Analyzer     B1+    58 (GSE level)

Average             B2/B2+    60

This suggests that the original prompt should include more detailed instructions about how the level of the report should be decided. Maybe something on the lines of:

Decide on the level of the recording/transcript on the CEFR scale, but don't reveal this and make sure the language used in the report will be understood by the learner who produced the recordings.