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    <title>audio-analysis on S Anand</title>
    <link>https://www.s-anand.net/blog/tag/audio-analysis/</link>
    <description>Recent content in audio-analysis on S Anand</description>
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      <title></title>
      <link>https://www.s-anand.net/blog/can-ai-hear-what-we-feel/</link>
      <pubDate>Thu, 25 Dec 2025 02:54:41 +0000</pubDate>
      <guid>https://www.s-anand.net/blog/can-ai-hear-what-we-feel/</guid>
      <description>&lt;p&gt;Gemini can pass the bar exam and solve maths olympiad puzzles. But it&amp;rsquo;s music-deaf.&lt;/p&gt;
&lt;p&gt;nitin kumar asked Gemini to rate 40 songs on joy, sadness, tension, nostalgia, etc. and compared it with human ratings. There was &lt;strong&gt;ZERO&lt;/strong&gt; correlation between the two. It&amp;rsquo;s like it&amp;rsquo;s a different species.&lt;/p&gt;
&lt;p&gt;In fact, if you just predict the average emotion for every single song, you&amp;rsquo;d still do 1.2× to 2× better than Gemini! It wasn&amp;rsquo;t adding noise to a signal. It was subtracting &lt;strong&gt;subtracting signal from noise&lt;/strong&gt;! In fact, for one song, the correlation was -88%, i.e. it predicted the exact opposite emotions.&lt;/p&gt;
&lt;p&gt;It&amp;rsquo;s not just noisy, it&amp;rsquo;s biased as well. It hears music as happier, more tender, more powerful than we do. It massively over-predicts &amp;ldquo;joyful activation&amp;rdquo; (53% of songs!) and dramatically under-estimates tension.&lt;/p&gt;
&lt;p&gt;The emotion predictions are suspiciously correlated with each other. Power and joy are basically identical (96% correlation).&lt;/p&gt;
&lt;p&gt;This confirms a suspicion I had: Gemini can&amp;rsquo;t actually hear the audio. It can transcribe, but beyond that it&amp;rsquo;s just guessing.&lt;/p&gt;
&lt;p&gt;Human music taggers are safe, for now.&lt;/p&gt;
&lt;p&gt;Story, prompts &amp;amp; analysis: &lt;a href=&#34;https://sanand0.github.io/datastories/llm-music/&#34;&gt;https://sanand0.github.io/datastories/llm-music/&lt;/a&gt;&lt;/p&gt;
&lt;p&gt;&lt;img loading=&#34;lazy&#34; src=&#34;https://files.s-anand.net/images/2025-12-25-can-ai-hear-what-we-feel-linkedin.jpg&#34;&gt;&lt;/p&gt;
&lt;p&gt;&lt;a href=&#34;https://www.linkedin.com/posts/sanand0_gemini-can-pass-the-bar-exam-and-solve-maths-activity-7409634892520546305-NdNi&#34;&gt;LinkedIn&lt;/a&gt;&lt;/p&gt;
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      <title>Experiments in sound</title>
      <link>https://www.s-anand.net/blog/experiments-in-sound/</link>
      <pubDate>Tue, 12 Sep 2006 12:00:00 +0000</pubDate>
      <guid>https://www.s-anand.net/blog/experiments-in-sound/</guid>
      <description>&lt;p&gt;Wikipedia says the human &lt;a href=&#34;http://en.wikipedia.org/wiki/Voice_frequency&#34;&gt;voice frequency&lt;/a&gt; for speech is between 85 to 155 Hz for men, and 165 to 255 Hz for women. That set me thinking.&lt;/p&gt;
&lt;ol&gt;
&lt;li&gt;What is the limit to our hearing?&lt;/li&gt;
&lt;li&gt;How do sounds differ?&lt;/li&gt;
&lt;li&gt;How can we synthesise speech?&lt;/li&gt;
&lt;/ol&gt;
&lt;p&gt;&lt;strong&gt;What are the limits to our hearing?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;Kids can hear frequencies from 20 Hz to 20 kHz, while adults hear only up to 12-14 kHz (&lt;a href=&#34;http://hypertextbook.com/facts/2003/ChrisDAmbrose.shtml&#34;&gt;Frequency Range of Human Hearing&lt;/a&gt;).&lt;/p&gt;
&lt;p&gt;To check the lower frequency limit, I created an MP3 with &lt;a href=&#34;https://files.s-anand.net/blog/a/lower.mp3&#34;&gt;sounds from 1 Hz to 100 Hz&lt;/a&gt; at 1 second intervals. Just play the sound, and see when you &lt;strong&gt;start&lt;/strong&gt; hearing something. (Of course, whether you can hear something also depends on the volume of your speaker, the ambient noise, etc.) I could hear nothing for the first 40 seconds: so I can&amp;rsquo;t hear frequencies lower than 40 Hz.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;PS: Don&amp;rsquo;t be worried if you don&amp;rsquo;t hear anything for a while. You&amp;rsquo;re not supposed to!&lt;/strong&gt; Keep the volume at full level, though.&lt;/p&gt;
&lt;p&gt;To check the upper frequency limit, I created this MP3 with &lt;a href=&#34;https://files.s-anand.net/blog/a/upper.mp3&#34;&gt;sounds from 1 kHz to 20 kHz&lt;/a&gt; in 1 second intervals. Just play the sound, and see when you &lt;strong&gt;stop&lt;/strong&gt; hearing anything. I couldn&amp;rsquo;t hear anything beyond 14 seconds: so I can&amp;rsquo;t hear frequencies beyond 14 kHz.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;How do sounds differ?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;I took this &lt;a href=&#34;https://files.s-anand.net/blog/a/vowels.mp3&#34;&gt;audio file of someone reciting vowels&lt;/a&gt; and plotted a spectrogram (below). A &lt;a href=&#34;http://www.google.com/search?q=define%3Aspectrogram&#34;&gt;spectrogram&lt;/a&gt; plots time on the X axis and frequency on the Y-axis.&lt;/p&gt;
&lt;p&gt;&lt;a href=&#34;https://www.s-anand.net/blog/assets/flickr-vowels-spectrogram_241586415_o-jpg.webp&#34;&gt;&lt;img alt=&#34;Vowels spectrogram&#34; loading=&#34;lazy&#34; src=&#34;https://www.s-anand.net/blog/assets/flickr-vowels-spectrogram_241586415_o-jpg.webp&#34;&gt;&lt;/a&gt;&lt;/p&gt;
&lt;p&gt;Some observations:&lt;/p&gt;
&lt;ul&gt;
&lt;li&gt;All the vowels have evenly spaced bars. (In this case, they&amp;rsquo;re all multiples of something around 120 Hz.)&lt;/li&gt;
&lt;li&gt;&amp;lsquo;u&amp;rsquo; has the lowest frequency mix. &amp;lsquo;a&amp;rsquo; spans from low to high. &amp;lsquo;i&amp;rsquo; has a bit of low and a bit of high, nothing in the middle. &amp;lsquo;ai&amp;rsquo; and &amp;lsquo;au&amp;rsquo; look like &amp;lsquo;a&amp;rsquo; followed by &amp;lsquo;i&amp;rsquo; and &amp;lsquo;u&amp;rsquo; respectively.&lt;/li&gt;
&lt;/ul&gt;
&lt;p&gt;&lt;strong&gt;How can we synthesise speech?&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;I don&amp;rsquo;t know. There are lots of speech synthesizers. They sound robotic. I&amp;rsquo;m trying to see if knowing what sounds look like improves things. I&amp;rsquo;ll let you know if I do well.&lt;/p&gt;
&lt;hr&gt;
&lt;h2 id=&#34;comments&#34;&gt;Comments&lt;/h2&gt;
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&lt;ul&gt;
&lt;li&gt;&lt;strong&gt;Dhar&lt;/strong&gt; &lt;em&gt;13 Sep 2006 5:09 am&lt;/em&gt;:
How did you go about synthesizing the MP3s with increasing frequencies? Did you use some software for that? Similarly what software did you use to plot the spectrogram?&lt;/li&gt;
&lt;li&gt;&lt;strong&gt;S Anand&lt;/strong&gt; &lt;em&gt;13 Sep 2006 6:10 am&lt;/em&gt;:
I wrote a &lt;a href=&#34;http://www.s-anand.net/a/sound&#34;&gt;perl script to generate the frequencies&lt;/a&gt;, and &lt;a href=&#34;http://www.hitsquad.com/smm/programs/SPECTROGRAM/&#34;&gt;Spectrogram v.0.8&lt;/a&gt; to create the spectrograms.&lt;/li&gt;
&lt;li&gt;&lt;strong&gt;Sumit Dhar&lt;/strong&gt; &lt;em&gt;16 Sep 2006 9:23 am&lt;/em&gt;:
Dude, just downloaded the files. Is the sound stereophonic or monoaural? If it is mono, do you think creating an MP3 with stereophonic sound will make a difference? Cheers, D.&lt;/li&gt;
&lt;li&gt;&lt;strong&gt;Sumit Dhar&lt;/strong&gt; &lt;em&gt;16 Sep 2006 9:25 am&lt;/em&gt;:
Loved the experiment. Lower: 42 Hz, Higher: 15 KHz&lt;/li&gt;
&lt;li&gt;&lt;strong&gt;S Anand&lt;/strong&gt; &lt;em&gt;16 Sep 2006 9:38 am&lt;/em&gt;:
It&amp;rsquo;s mono. I doubt if stereo would make a difference. I&amp;rsquo;d be playing the same frequency on both speakers, which is what a mono MP3 does anyway.&lt;/li&gt;
&lt;li&gt;&lt;strong&gt;Dhar&lt;/strong&gt; &lt;em&gt;17 Sep 2006 2:05 am&lt;/em&gt;:
The reason I asked about whether the sound is Mono or Stereo is because of my experience during eye tests. Some letters that were not visible when viewed with just &lt;strong&gt;one&lt;/strong&gt; eye, were clearly readable when using both eyes. Was wondering if the same &lt;strong&gt;may&lt;/strong&gt; be applicable in this case?&lt;/li&gt;
&lt;li&gt;&lt;strong&gt;S Anand&lt;/strong&gt; &lt;em&gt;17 Sep 2006 7:36 am&lt;/em&gt;:
Ah, I see what you mean. Since both speakers would be playing the sound, hopefully this should not be a factor.&lt;/li&gt;
&lt;/ul&gt;
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    <item>
      <title>Hacking using keyboard whispers</title>
      <link>https://www.s-anand.net/blog/hacking-using-keyboard-whispers/</link>
      <pubDate>Wed, 12 May 2004 12:00:00 +0000</pubDate>
      <guid>https://www.s-anand.net/blog/hacking-using-keyboard-whispers/</guid>
      <description>&lt;p&gt;It&amp;rsquo;s possible to make sense out of &lt;a href=&#34;http://searchsecurity.techtarget.com/originalContent/0,289142,sid14_gci963348,00.html&#34;&gt;keyboard whispers&lt;/a&gt;.&lt;/p&gt;
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