How to change audio recording settings to 16Khz and 16 bit when we record audio?

Question

I have the settings shown below.

I want change audio recording settings to 16Khz and 16 bit when we record audio.

NSArray *dirPaths;
NSString *docsDir;

dirPaths = NSSearchPathForDirectoriesInDomains(
                                               NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];
NSString *soundFilePath = [docsDir
                           stringByAppendingPathComponent:@"sound.wav"];

NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath];

NSDictionary *recordSettings = [NSDictionary
                                dictionaryWithObjectsAndKeys:
                                [NSNumber numberWithInt:AVAudioQualityMin],
                                AVEncoderAudioQualityKey,
                                [NSNumber numberWithInt:16],
                                AVEncoderBitRateKey,
                                [NSNumber numberWithInt: 2],
                                AVNumberOfChannelsKey,
                                [NSNumber numberWithFloat:44100.0],
                                AVSampleRateKey,
                                nil];

NSError *error = nil;

audioRecorder = [[AVAudioRecorder alloc]
                 initWithURL:soundFileURL
                 settings:recordSettings
                 error:&error];

if (error)
{

} else
{
    [audioRecorder prepareToRecord];
}

How to set those settings?

Edit the question:

Thanks for giving the replies, i tried those ways but it did not work for me, Because my client is sending the recorded voice(the recorded voice what i am sending in bytes format) to ASR engine (Automatic speech recognition). i am not getting back the same response (i am getting the response audio says "quotation mark") what i send . Client says you are not recording the voice in 16KHz and 16 bit sample rate thats why you are getting that response. But i asked him the bytes what i send to his server, He given that .wav file it is playing perfectly. But if the same one he is sending to ASR engine , the ASR engine not accepts the recorded voice what i am sending(He says that ASR wont accept because you are not recording audio in 16KHz and 16 bit sample rate). Client given the following response. (But, I tried all the ways suggested by you)

Filename:   sv_SE_356985580762248932.wav
Folder: E:\developApp\TestappName\Mortionsn_dev\2nd-iteration\test_wfiles
File Type:  44100Hz, 16-bit, Stereo
Uncompressed Size:  1.63 MB (1,713,696 bytes)
File Format:    Windows PCM
Windows PCM
Size on Disk:   1.63 MB (1,717,892 bytes)
Last Written (local):   3/11/2013  00:21:00.000
Length: 0:09.714
428,424 samples

Edit the question 2nd Time By using Below Answers:

Later by giving the suggestions i changed my settings code to:

NSMutableDictionary *recordSettings = [NSMutableDictionary dictionary];


[recordSettings setValue: [NSNumber numberWithInt:kAudioFormatLinearPCM] forKey:AVFormatIDKey];

[recordSettings setValue: [NSNumber numberWithFloat:16000.0] forKey:AVSampleRateKey];//8000.0

[recordSettings setValue: [NSNumber numberWithInt: 1] forKey:AVNumberOfChannelsKey];

[recordSettings setValue: [NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];

[recordSettings setValue: [NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey];

[recordSettings setValue: [NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey];

[recordSettings setValue: [NSNumber numberWithInt: AVAudioQualityMax] forKey:AVEncoderAudioQualityKey];

Answer 1

Your existing settings are 44.1kHz and 16 bit so (assuming the above already works) the only line you'd need to change is:

[NSNumber numberWithFloat:44100.0] 

To:

[NSNumber numberWithFloat:16000.0]

Answer 2

Try this, General Audio settings are,

AVFormatIDKey,
AVSampleRateKey,
AVNumberOfChannelsKey.

And for Audio recorder

AVEncoderAudioQualityKey;
AVEncoderBitRateKey;
AVEncoderBitRatePerChannelKey;
AVEncoderBitDepthHintKey;

make sure you have included general and recorder settings.

and change your AVSampleRateKey to 16000.0,

NSDictionary *recordSettings = [NSDictionary dictionaryWithObjectsAndKeys:                 
                                [NSNumber numberWithInt:kAudioFormatLinearPCM],
                                AVFormatIDKey
                                [NSNumber numberWithInt: 2],
                                AVNumberOfChannelsKey,
                                [NSNumber numberWithFloat:16000.0],
                                AVSampleRateKey,
                                [NSNumber numberWithInt:AVAudioQualityMin],
                                AVEncoderAudioQualityKey,
                                [NSNumber numberWithInt:16],
                                AVEncoderBitRateKey,
                                nil];